ATLAS OF NORTHWESTERN MEDITERRANEAN COCCOLITHOPHORES

The present Atlas contains a detailed study, based in scanning electron microscopy (SEM) observations, of living coccolithophores from NW Mediterranean waters. The study contains 103 figures with 411 micrographs, which correspond to 168 coccolithophores (including different taxonomic and morphotypic entities). The figured specimens were collected during different cruises carried out from 1995 to 1999.Classification of the organisms follows modern taxonomy of living calcareous nannoplankton. Measures of the specimens and notes on their taxonomy are given in addition to abridged descriptions of the studied taxa. The atlas contains a large number of previously undescribed forms, specially in the genera Syracosphaera, Papposphaera, Polycrater, Anthosphaera, Corisphaera and Sphaerocalyptra . Several species never illustrated in the literature are presented here for the first time. Coccospheres having coccoliths of different recognized species are presented. These combination coccospheres are nowadays considered as transitional steps between different phases in the cellular life-cycle. An introduction with a brief overview of the actual coccolithophore knowledge and an abridged glossary with figures of the basic terminology are included.


INTRODUCTION
These pages consider coccolithophores, a group without rigorous taxonomic meaning, as embracing all (golden-brown) microalgae which at least at some point in their life cycle, produce and bear coccoliths. The coccoliths are minute, delicate and very beautiful scales of calcium carbonate which make an important contribution to transport of the inorganic carbon produced in pelagic areas to the ocean floor and thus to the sedimentary archive. Since they are biologically-formed and sediment-forming, coccol-iths are extremely valuable for stratigraphic and paleoceanographic purposes; they have been extensively used as stratigraphic fossils in sediments of Jurassic to Quaternary age (Perch-Nielsen, 1985 a, b;Bown, 1998) and detailed chronostratigraphic and paleoecological reconstructions have been successfully established (e.g. the studies of NW Mediterranean Pliocene sediments by Matias, 1990, and of W Mediterranean Pleistocene-Holocene sediments by Flores et al. 1997).
The coccolithophores play key roles in global biogeochemical cycles, particularly in the carboncarbonate cycle (Honjo, 1976;Westbroek, 1991;Westbroek et al., 1994), but also in the sulphur cycle SUMMARY: The present Atlas contains a detailed study, based in scanning electron microscopy (SEM) observations, of living coccolithophores from NW Mediterranean waters. The study contains 103 figures with 412 micrographs, which correspond to 168 coccolithophores (including different taxonomic and morphotypic entities). The figured specimens were collected during different cruises carried out from 1995 to 1999. Classification of the organisms follows modern taxonomy of living calcareous nannoplankton. Measures of the specimens and notes on their taxonomy are given in addition to abridged descriptions of the studied taxa. The atlas contains a large number of previously undescribed forms, specially in the genera Syracosphaera, Papposphaera, Polycrater, Anthosphaera, Corisphaera and Sphaerocalyptra. Several species never illustrated in the literature are presented here for the first time. Coccospheres having coccoliths of different recognized species are presented. These combination coccospheres are nowadays considered as transitional steps between different phases in the cellular life-cycle. An introduction with a brief overview of the actual coccolithophore knowledge and an abridged glossary with figures of the basic terminology are included.
since they produce dimethylsulphoniopropionate (DMSP), the precursor of dimethyl sulphide (DMS) (Keller et al., 1989;Malin and Kirst, 1997) which may influence climate through stimulating cloud formation and influencing the Earth's radiative balance (Charlson et al., 1987;Simó and Pedrós-Alió, 1999). Some coccolithophores are known to produce stable lipid compounds which can be used as a tool to evaluate paleoclimatic changes (Volkmen et al., 1980;Brassell et al., 1986). These properties, together with the fact that the ubiquitous species Emiliania huxleyi is a recognized bloom-forming alga (Holligan et al., 1993), confer on the coccolithophores an important role as active biogeochemical and climatic agents.

First records
The first recorded observation of elliptical, flattened discs, having one or several concentric rings on their surface, was made by C.G. Ehrenberg in 1836 while examining Cretaceous chalk from the island of Rugen in the Baltic Sea. Later, in 1858, T.H. Huxley, working with North Atlantic sediments, was the first to name these small structures 'coccoliths'. Both authors, Ehrenberg and Huxley, considered these platelets as of inorganic origin. G. C. Wallich observed coccospheres in a sample from salp gut, collected on his return from India in 1857. From a study of English chalk in 1860, H. C. Sorby (1861) realized that the small discs were concave on one side and convex on the other and predicted, and later found, that coccoliths were united as small, hollow spheres in the chalk. Like Wallich, Sorby believed that these coccospheres had an organic origin. The first living coccolithophores, Coccosphaera pelagica and Coccosphaera carterii, were described by Wallich (1877) as free-floating cells. Numerous studies have subsequently been made, using both the light microscope (LM) and later using the techniques of transmission electron microscopy (TEM) and scanning electron microscopy (SEM) (see Siesser, 1994, for a detailed review of the early studies on coccolithophores).

The living cell, reproduction and life cycles
The coccolithophore cell Coccolithophores are typically marine, planktonic, unicellular, biflagellate cells which are surrounded by coccoliths and also have an haptonema, but they can exist without one or several of these characters. Cell size is usually between 3 and 30 µm and cells may be spherical, subspherical, ovoid to oval or obpyriform in shape, but can take other forms, sometimes being elongated and even spindle-shaped (Heimdal, 1993;Young et al., 1997). Detailed cytological investigations have been undertaken, including studies of the formation of coccoliths and scales (Klaveness and Paasche, 1971;Inouye and Pienaar, 1984;Inouye and Pienaar, 1988;Fresnel, 1989;Fresnel and Billard, 1991) and detailed descriptions of complex organelles such as the haptonema (Inouye and Kawachi, 1994). Two structurally very different types of coccoliths, heterococcoliths and holococcoliths, formed by different types of biomineralisation, are recognizable. The heterococcoliths are formed by crystal-units of variable shape and size, and their biomineralisation, initiated by nucleation of a proto-coccolith ring, occurs intracellularly (Manton and Leedale, 1969;Inouye and Pienaar, 1988;Westbroek et al., 1989;Young, 1989;Fresnel, 1989, Fresnel andBillard, 1991;Pienaar, 1994). The holococcoliths are formed of numerous minute (<0.1 µm) crystallites; their calcification appears to occur extra-cellularly (Manton and Leedale, 1963;Klaveness, 1973;Rowson et al., 1986), but within the periplast (on the periplasmic side of the plasma membrane, de Vrindde Jong et al., 1994). Rowson et al. (1986) showed that the periplast of a holococcolithophore is composed of a layer of columnar material, several layers of scales, crystalloliths and an external membrane layer called the envelope, which seems to be responsible for crystalolithogenesis.
The studies of von Stosch (1967), Parke and Adams (1960), Klaveness and Paasche (1971) and Fresnel (1989) have shown that coccolithophores of very different types can be involved in highly complex life cycles (Billard, 1994). Parke and Adams (1960) demonstrated that monoclonal strains of the heterococcolithophore Coccolithus pelagicus (Wallich) Schiller can give rise to what previously was believed to be a distinct species; the holococcolithophore Crystallolithus hyalinus Gaarder et Markali. In studies on shadowcasted material, Leedale (1963, 1969) found different patterns on the body scales of these two life stages, leading to speculation about the existence of a haplo-diploid life cycle, where the Coccolithus pelagicus cells would be diploid, whereas those named Crystallolithus hyalinus would be haploid (Billard, 1994). In addition, Rowson et al. (1986) showed that two distinct holococcolith morphologies could be produced, the typical 'Crystallolithus hyalinus' type and a more fenestrate type which had previously been described as a separate species, Crystallolithus braarudii Gaarder 1962. Life cycles involving coccolith and non-coccolith-bearing phases have been well documented, particularly in the coastal genera of the families Pleurochrysidaceae and Hymenomonadaceae. Studies on the species now known as Pleurochrysis carterae (Braarud et Fagerland) Christensen revealed an elaborate life cycle with a diploid heterococcolith bearing phase, including both motile and non motile stages, and an haploid benthic pseudofilamentous phase (Apistonema stage in the sense of von Stosch, 1967). This non-motile phase may form naked swarmers or motile gametes, which fuse to form a zygote which develops coccoliths. Both phases appear to have an unlimited capacity for vegetative reproduction (Rayns, 1962;Leadbeater, 1970). Gayral and Fresnel (1983) observed both meiotic division and syngamy in the life cycle of Pleurochrysis pseudoroscoffensis. Culture studies have demonstrated that the heterococcolithophore phase of these life-cycles is diploid and the benthic noncalcifying phase is haploid, and that each phase has a characteristic microfibrillar pattern on the organic body scales (Fresnel, 1989(Fresnel, , 1994Fresnel and Billard, 1991).
Emiliania huxleyi presents an interesting life cycle with coccolith-bearing cells (the C-cells) and non-coccolith-bearing stages (the naked N-cells and the scale-bearing swarmer S-cells), each cell type being capable of independent vegetative reproduction (Klaveness and Paasche, 1971). In addition, amoeboid cells can be found occasionally in cultures of C-, N-and S-cells and extremely large cells can be found in old cultures (Klaveness, 1972b). Flow cytometric analysis has shown that the C-cells have a DNA content twice that of the Scells . C-and N-cells are presumably diploid cells whilst the S-cells might represent the haploid stage (Paasche and Klaveness, 1970;Green et al., 1996).

Combination coccospheres recorded from plankton samples
Besides the well documented combination specimens of Coccolithus pelagicus -Crystallolithus hyalinus, as quoted above, other combinations have occasionally been observed in plankton samples. Some of these specimens have been clearly documented with SEM images, but others have been admirably recorded, despite considerable technical difficulties, with LM techniques.
Among natural specimens examined by LM, Kamptner (1941) described, and in some cases illustrated, several combination or 'hybrid' coccospheres ("Individuen mit kombinierter Schale"). He gave a detailed account of various combinations of heterococcolithophore Syracosphaera species with holococcolithophores, particularly of two living cells exhibiting coccoliths of both Syracosphaera tuberculata Kamptner (now known as Coronosphaera mediterranea (Lohmann) Gaarder) and Zygosphaera wettsteinii Kamptner (now Calyptrolithina wettsteinii (Kamptner) Norris). He noted the similarity of his observation of Calyptrosphaera oblonga combining with big coccoliths (possibly of Syracosphaera) with the drawings of Lohmann (1902), and among other findings, observed several combination specimens of Anthosphaera robusta with Calyptrosphaera quadridentata. Moreover he described the association of two holococcolithophores: Corisphaera gracilis Kamptner with Zygosphaera hellenica Kamptner. Lecal-Schlauder (1961), also using LM, recorded four more combinations. One combination (not figured) is described as a specimen bearing coccoliths of both Syracosphaera pulchra Lohmann and Calyptrosphaera pirus Kamptner (now, Daktylethra pirus (Kamptner) Norris). The other hybrid cells are figured and one appears to combine both Helicosphaera carteri coccoliths and holococcoliths tentatively identifiable as Syracolithus confusus; another is an obpyriform coccosphere of Calyptrosphaera oblonga also bearing big heterococcoliths which are difficult to identify since they are seen in proximal view behind the thickness of the coccosphere; the last is recorded as a combination of Acanthoica acanthos Schiller with Syracosphaera aperta Schlauder.
Among natural specimens examined by SEM, Kleijne (1991) found a composite cell of the heterococcolithophore Calcidiscus leptoporus (Murray et Blackman) Loeblich Jr. and Tappan and the holococcolithophore Crystallolithus rigidus Gaarder; this association has been repeatedly figured in recent publications (Cortés, 2000;Renaud and Klaas, 2001) and it has been observed in culture (I. Probert, pers. comm.). In addition, a spectacular combination coccosphere composed of a complete coccosphere of Calcidiscus leptoporus surrounded with coccoliths of Syracolithus quadriperforatus (Kamptner) Gaarder has been found in the Alboran Sea, W Mediterranean (Geisen et al. 2000). Kleijne (1991) also recognized an association of Syracosphaera sp. type A with a holococcolithophore bearing both laminar ordinary coccoliths and zygolith-like circum-flagellar coccoliths. Thomsen et al. (1991), examining natural Arctic samples with TEM techniques, recognized cells of the heterococcolithophore genera Papposphaera Tangen, Pappomonas Manton and Oates and Wigwamma Manton, Sutherland and Oates that included or combined elements typical of the holococcolithophore genera Turrisphaera Manton, Sutherland and Oates, Trigonaspis Thomsen and Calciarcus Manton, Sutherland and Oates respectively.
The well established association of Coccolithus pelagicus with Crystallolithus hyalinus was found in Arctic surface waters and figured in a SEM micrograph by Samtleben and Schröder (1992); another specimen with C. pelagicus heterococcoliths covered by holococcoliths of Crystallolithus hyalinus is figured by Samtleben in Winter and Siesser (1994) and in Samtleben et al. (1995). Alcober and Jordan (1997) presented for the first time an association, found in natural samples from the central North Atlantic, involving elements of the heterococcolithophore Neosphaera coccolithomorpha Lecal-Schlauder with the nannolith bearing species Ceratolithus cristatus Kamptner. This association was subsequently found on two further occasions by Young et al. (1998). Recently, Sprengel and  represented the combination of Ceratolithus cristatus, Neosphaera coccolithomorpha coccoliths and hoop-like cocccoliths (i.e. all the known coccoliths of Ceratolithus cristatus being together).
During the present study several combination coccospheres showing known associations and several more with new associations were found from NW Mediterranean waters. These specimens, most of which are already published in Cros et. al. (2000b), are figured in the present atlas.

Classification and taxonomic status
Despite increasing awareness of the limitations involved, coccolith morphology still remains the most important character in the classification of the coccolithophores. Distinct coccolith types have been recognized and the species, genus and family concepts formed around them (Jordan et al., 1995). The coccolithophores are difficult to classify, as testified by the numerous changes that the taxonomy of this group has experienced in the higher (see a revision in Cros, 2001) and in the lower taxonomic ranks (see below). Nevertheless the families as accepted here behave as robust taxa (Jordan and Green, 1994) and they have been universally accepted as the main level of classification (Young and Bown, 1997a), to which relatively few changes have been introduced in recent years. Braarud et al. (1955) classified the coccoliths into three groups: heterococcoliths, holococcoliths and pentaliths. The latter group is now included, in broader grouping nannoliths (Young and Bown, 1997a). The heterococcoliths, formed by crystalunits of complex shape, are well structured and well represented in the fossil record. Their structural inter-specific differences are generally large and are used to characterize species, genera and families. The holococcoliths, constructed of numerous minute calcite crystals, are easily disintegrated; their fossil record is not so good and their classification is difficult (Kleijne, 1991) with differentiation above the genus level generally not possible. Holococcolithophores (coccolithophores that present only holococcoliths, according to present knowledge) are grouped into a single family, the Calyptrosphaeraceae (Kleijne 1991, Jordan andYoung and Bown, 1997b) although it is increasingly apparent that this is an artificial grouping.

Terminology
Since the taxonomy of calcareous nannoplankton is based on the morphological characters of the coccoliths, the adopted terminology of coccolith parts has always been important. The development of electron microscopy permitted much greater resolution of the structural details of coccoliths, leading to the necessity for a review of previous terminology. A co-operative effort to compile and standardize the new nomenclature was made by several authors (Braarud et al., 1955;Halldal and Markali, 1955;Hay et al., 1966) and other authors have included in their papers glossaries or terminological explanations (Perch-Nielsen, 1985a,b;Heimdal, 1993;Kleijne, 1993). Three work sessions have even been held concerning this subject: a round table session at the 1970 Rome Plankton Conference (Farinacci, 1971), a terminology workshop held during the International Nannoplankton Association (INA) conference in Prague, 1991, and the subsequent terminology working group meeting held in London in 1992 (Young, 1992b). The last two workshops yielded syntheses of descriptive terminology (Jordan et al., 1995;Young et al., 1997) which are essentially followed in the present study.

Objectives of the present atlas
The main objective of the atlas is to illustrate the coccolithophore species present in NW Mediterranean waters using Scanning Electron Microscopy (SEM) micrographs. In the course of examining the samples collected, many species identification problems were encountered, prompting a taxonomic survey of the literature.

Sampling techniques
The water samples were collected at selected depths using a rosette with Niskin bottles attached to a Conductivity, Temperature, Depth (CTD) probe, except during the Meso-95 cruise, when surface water was sampled with a bucket. In the 1995 cruises, all of the samples were fixed with neutralized formaldehyde except in four stations where parallel samples were filtered on board without fixation in order to compare the results. The best results were obtained without fixation of the material. Loss of holococcolithophore species and poor preservation of some heterococcolithophores were clearly observed in the fixed samples (Cros, 2001). After-wards, knowing the risk to lose coccolithophores using fixation methodologies, all the samples were directly filtered on board without adding chemicals.

Filtration methodology
About 200 ml of sea water were filtered, using a vacuum pump, onto polycarbonate Nucleopore filters of 0.8 µm pore size and 25 mm diameter (Kleijne, 1991, considers that polycarbonate membrane filters, with their smooth surface, have the best properties to allow observation of the smallest coccolithophores in the SEM). Another filter with pore size of 3 µm (usually Millipore cellulose acetate nitrate) was placed below the Nucleopore filter, in order to ensure an even distribution of filtered particles. Salt was removed by washing the filters with about 2 ml of bottled drinking water (pH 7.9 -8.3). The filters were air dried and stored under partial vacuum in hermetically closed boxes until preparation for the Scanning Electron Microscope (SEM).

Microphotographs and measurements
A part of the filter was placed on a SEM stub and coated with a film (about 150 Å thick) of gold or gold-palladium to avoid electric charges; the sputter coater used was a Polaron SC-500. The examination and microphotography of the specimens were conducted in a Hitachi S-570 Scanning Electron Microscope.
The coccosphere and coccolith measurements as well as the enumeration of the number of coccoliths were made on the available micrographs, which had been obtained for taxonomic purposes. The measurements, where possible, were taken from several specimens and the numbers recorded reflect the minimum and maximum as well as the most common values obtained (always in µm). Where measures are reported from other authors or from other areas, the reference is given next to the number.

Basic nomenclature
Before introducing the adopted classification, the most common terms used when describing coccolithophores and in particular their coccoliths are reviewed. More detailed terminological information can be found in the literature quoted above (Terminology, Introduction).

Coccolithophores and coccospheres
In a motile coccolithophore cell (Fig. 4), the coccosphere composed of coccoliths has a flagellar opening in the apical pole through which emerge the two flagella and the haptonema. In some coccospheres the coccoliths around the flagellar opening are morphologically differentiated, in which case they are termed circum-flagellar coccoliths (in contrast to the body coccoliths which constitute the rest of the coccosphere). Some coccolithophores also possess differentiated coccoliths in the antapical pole, termed antapical coccoliths. The coccospheres of some coccolithophores, members of the genus Syracosphaera for example, consist of two layers of coccoliths; the inner endotheca and an external layer, the exotheca, characterised by a very different kind of coccoliths. Such coccospheres are termed dithecate (Fig. 5), in contrast to monothecate coccospheres, which possess only one coccolith layer. When several layers of the same kind of coccoliths are present, as is often the case in Emiliania huxleyi for example, the coccosphere is described as being multilayered.
In the literature, an endotheca which has only one kind of coccoliths is qualified as monomorphic; if it has two different kinds of coccoliths it is termed dimorphic, and if it has three or more kinds, as polymorphic. When gradual morphological dif-ferences between coccoliths at the apical and antapical poles are observed, the coccosphere is described as being varimorphic.
The shape of coccospheres has been used as a character for coccolithophore classification, particularly in early descriptions using light microscopy (LM) techniques. With the advent of electron microscopy (TEM and SEM) the morphology of the coccoliths has become the most important character in the classification of the coccolithophores, and indeed the shape of coccospheres has been demonstrated not to usually be a constant and conclusive character.

Coccoliths
The most common form of coccoliths (especially of those found in sediments and fossil deposits) are the heterococcoliths, formed of complex arrays of crystal units typically arranged in rings (cycles) (Fig. 6A). Heterococcoliths have two morphologically differentiated parts, the central-area and the rim (Figs. 7 and 8). The central area can be unfilled or possess different types of elements (e.g., radial laths, rods, etc) or even have highly elaborated structures or spines (Young 1992a). Can be recognized three principal morphologically different heterococcolith types: planoliths, muroliths and placoliths (Young 1992b, Young et al. 1997. These types essentially differ in having the rim at different angles relative to the central area: (a) in the same plane (planoliths); (b) with all or most of the rim perpendicular or sub-perpendicular to the centralarea (muroliths); and (c) with a small part of the rim perpendicular, and two well developed parts, the shields, parallel to the central area (placoliths) (Fig.  7). It should be noted that a murolith without flanges resembles a planolith with the rim bent upwards, and that a placolith can have the appearance of a murolith with two well developed flanges. Placoliths form the most robust coccospheres, their structure allowing tight interconnection and hence the formation of a compact case.
In addition to heterococcoliths and holococcoliths, a third type of calcified structure are the nannoliths (Fig. 6C), which were originally defined, by exclusion, as calcareous nannofossils lacking the typical features of calcareous dinophytes, heterococcoliths or holococcoliths and so of uncertain affinity (Perch-Nielsen, 1985). Nowadays the same name, by extension, can be applied to a few living taxa where the calcareous structures are not definitely homologous (even architecturally) with heterococcoliths or holococcoliths e.g. Braarudosphaera (pentaliths), Florisphaera (plates), Ceratolithus (ceratoliths), Polycrater (usually bowl-shaped coccoliths) (Young, 1992b;Young and Bown, 1997a;Bown and Young, 1998).

General taxonomic list and abridged descriptions of the observed species
The formal classification of coccolithophores is in a state of flux. The present classification scheme, one of several possible today, follows essentially Cavalier-Smith (1998), Edvarsen et al. (2000 and Young and Bown (1997a, b) for the higher classification; Jordan and Kleijne (1994) and Jordan and Green (1994) for family and lower ranks and Kleijne (1991) and Kleijne (1992) for the families Calyptrosphaeraceae and Rhabdosphaeraceae respectively. The published PhD thesis of Kleijne (1993) and the publications of Perch-Nielsen (1985a, b), Chrétiennot-Dinet (1990) Heimdal (1993 and Bown (1998) have been of valuable help. The descriptions are focussed on contributing to knowledge of the limits and variability of each species. All measures, coccolith counts, shapes, etc. refer to the specimens actually observed in the Mediterranean through the present study. Since it is generally not possible to count all coccoliths on a given coccosphere, estimates of the coccolith numbers on the total coccosphere are given, based on counts of coccoliths on the visible parts of the coccosphere. The annotated dimensions, always in µm, of both coccospheres and coccoliths refer to the long axis if no other indication is given. A question mark next to a reference indicates that the mentioned species may be, or is, morphologically similar to the studied species.
The taxa referred to with the epithet "sp." are not known to science or not recognized, at present, from the older light microscopy descriptions; these taxa, whenever possible, will be described as new species, or redescribed on the basis of SEM images, in further publications.  Young, 1992b andYoung et al., 1997) FIG. 8. -A murolith with flanges in distal view and side view. This murolith has the central area filled with laths, and hence is termed a caneolith. The connecting external ring, a character useful for the classification of caneoliths, morphologically belongs to the central area but structurally belongs to the rim corresponding to the inner rim of rhabdoliths (see coccolith structure of the Rhabdosphaeraceae in Kleijne, 1992 PRYMNESIOPHYCEAE Hibberd 1976emend. Cavalier-Smith, 1996. Subclass PRYMNESIOPHYCIDAE Cavalier-Smith 1986emend. Cavalier-Smith, 1996(in Cavalier-Smith et al., 1996 Order ZYGODISCALES Young and Bown 1997 The heterococcoliths are muroliths, and modified derivatives, with an outer rim with anticlockwise imbrication and an inner rim with clockwise imbrication. Central area structures include transverse bars, diagonal crosses and perforate plates but no spines.
Cells normally bearing heterococcoliths in at least one stage of their life-cycle (Jordan and Green, 1994). A member of this family, Helicosphaera carteri, has been shown to form combination coccospheres with holococcoliths .
Extant species are motile, forming ellipsoidal coccospheres with a prominent flagellar opening (Young and Bown, 1997b). The characteristic heterococcolith of this family is the helicolith with the outer rim modified into a helical flange, ending in a wing or spike.
Genus Helicosphaera Kamptner, 1954 Ellipsoidal coccospheres with coccoliths arranged spirally around the coccosphere in a characteristic manner. The heterococcoliths, called helicoliths, have a characteristic helical flange. Species and subspecies can be recognized based on presence/absence of a conjunct or disjunct bar (a bar formed from the rim or not, respectively), bar orientation and flange shape (Young and Bown, 1997b).
The coccoliths, termed helicoliths, usually possess a conjunt transverse bar separating two aligned openings in the central area and a well developed wing in the distal flange.
Since coccospheres bearing this morphotype and the perforate morphotype have been observed (Cros et al., 2000, and Figs. 11C, D) we infer that this variation is ecophenotypic rather than genotypic. It may prove ecologically significance to distinguish these morphotypes but we do not regard them as discrete taxa.
The helicoliths of this variety have two offset slit-like openings instead of the two central openings arranged in a horizontal line present in H. carteri var. carteri.
Transitional shapes between H. carteri v. carteri and H. carteri v. wallichii exist, even on the same coccosphere, as reported by Jordan and Young (1990) and Kleijne (1993) and illustrated by Nishida 1979, pl. 9 Fig. 4a, b, c. Even Okada andMcIntyre (1977), who described H. wallichii new comb., remarked that the separation at species level was tentative due to the occasional specimens showing transitional forms between these two types.

Helicosphaera pavimentum
Thin helicoliths with narrow spiral flange and one or two central perforations or one or two aligned slits present or absent. These helicoliths resemble particularly the helicoliths of H. carteri var. hyalina but are smaller and thinner and have a narrower flange. We infer that this is a discrete species.
Family PONTOSPHAERACEAE Lemmermann, 1908 Cells normally bearing heterococcoliths in at least one stage of their life-cycle (Jordan and Green, 1994). Extant species apparently non-motile, coccospheres subspherical and they may have highlymodified equatorial coccoliths (Scyphosphaera). The coccoliths have an outer rim with a very clear anticlockwise imbrication. The characteristic heterococcolith of this family is the discolith, also named cribrilith, which is a murolith without flanges possessing roundish pores in the central area; the possession or not of lopadoliths, large equatorial barrel-shaped coccoliths, separates the two extant genera, Scyphosphaera and Pontosphaera.
Close affinty of the Helicosphaeraceae and Pontosphaeraceae is not obvious from coccolith morphology but was inferred from palaeontological studies (Romein, 1979;Aubry, 1989) and has been confirmed by molecular genetics (Saez and Medlin, pers. comm.).

Scyphosphaera apsteinii f. dilatata
The coccosphere figured in 13C has a lopadolith inside it, but since the lopadolith is partially covered by cribriliths, it is not possible to definitively establish whether its width decreases distally. Further work might prove that S. apsteinii f. dilatata is merely an early developmental form of S. apsteinii f. apsteinii. Siesser (1998) argues that the three supposedly different species, Scyphosphaera cohenii, S. antilleana and S. apsteinii f. dilatata can be considered conspecific. In the belief that in the near future it should be proven that S. apsteinii f. dilatata belongs to S. apsteinii f. apsteinii, it can be wise to maintain the dilatata form related to S. apsteinii species and not to transfer it to S. cohenii.
Order STEPHANOLITHIALES Bown and Young 1997 The coccoliths are muroliths with the wall composed of non-imbricating elements, i.e. in side-view, the sutures are vertical or near-vertical (Bown and Young, 1997) Family CALCIOSOLENIACEAE Kamptner, 1927 Extant species have elongate fusiform coccospheres, which may possess spine-bearing polar coccoliths. Coccoliths are rhomboidal muroliths (named scapholiths), which diminish in width towards the poles where they justify the name of scapholiths (in the poles, the coccoliths are like a "skaphos", boat). The scapholiths are muroliths without flanges; the central area has laths with a perpendicular disposition to the major diagonal and no a differentiated central structure is present. This family has very clear and unmistakable characteristics, but the systematics at generic and specific level are not easy (Black, 1968;Manton and Oates, 1985). It is clear that in the future much work is necessary to attempt to clarify how many and which species make up this family. In the present study the specimens were measured with great precision to perceive differences in the studied taxa.
It is interesting to remark that this family has representatives from the early Cretaceous to the Holocene, but without stratigraphic interest due to the sporadic nature of their occurrence. Perch-Nielsen (1985a, b) points out that Scapholithus fossilis and Anaplosolenia brasiliensis are two of the few species that survived the event(s) of the Cretaceous/Tertiary boundary.

Anoplosolenia brasiliensis
In the quoted literature, as in the present study, differences in coccosphere and coccolith size and number and wideness of the laths, as well as presence or absence of enlargements in the pointed tip of the rhomboidal coccoliths are observed. For this reason more work is necessary on this genus to determine if the differences among the specimens could permit recognition of different species or if only one species with gradational differences exists.
The species A. brasiliensis was described by Lohmann (1919) under the name Cylindrotheca brasiliensis, a confusion based on its similarity to diatoms of the genus Cylindrotheca. When Halldal and Markali (1955) described the coccoliths, using TEM techniques, they remarked that the coccol-iths shown by Deflandre and Fert (1953) were somewhat smaller in size than their observations. In the present study the coccoliths of Anaplosolenia specimens more closely resemble those described by Deflandre and Fert (1953), having less (around 40 compared to more than 50) but wider laths than the specimens observed by Halldal and Markali (1955) and Gaarder and Hasle (1971).
Genus Calciosolenia Gran, 1912 Large-sized coccosphere with tapering ends and bearing polar spine-like coccoliths. This genus differs from Anaplosolenia in being slightly smaller, in having more abruptly tapering ends and in possessing long polar spine-like coccoliths. Gran, 1912 (Figs. 15A-D) In the present study all fusiform coccospheres with spine-bearing polar coccoliths and having the rhomboidal coccoliths with real laths or plate-like laths are reported as C. murrayi.

Calciosolenia murrayi
The coccospheres are shorter and the scapholiths are larger than those of Anoplosolenia brasiliensis, and long spines are present on apical and antapical poles.
Order SYRACOSPHAERALES HAY 1977 This order, embracing Syracosphaeraceae and Rhabdosphaeraceae, groups taxa which basically bear muroliths, planoliths or both together. The coccospheres can exhibit different kinds of coccoliths in only one theca, or in different thecas and even, several species of the genus Syracosphaeraceae, can have jointly dithecatism and polymorphic coccoliths in the endotheca. A distinctive radial lath cycle is a common feature of body coccoliths in Syracosphaeraceae and in most of the species of Rhabdosphaeraceae. Representatives of both families, Syracosphaeraceae and Rhabdosphaeraceae, present hetero-holococcolithophore combination coccospheres.
Family RHABDOSPHAERACEAE Haeckel, 1894 The coccoliths of this family are named rhabdoliths, a name first employed to designate coccoliths with a central styliform process, but since extended to include all coccoliths with the distinctive rim structure of the family (Kleijne, 1992).
The body coccoliths have the rim formed of two rings of elements and a central area consisting of one to several rings (cycles) of different types of elements, which are disposed in the following order from the external to inner part: radial laths, lamellae elements, needle-shaped/elongated elements, tile shaped elements and cuneate elements. Central area often with a conical or sacculiform shape or having a robust spine.
Some representatives of this family, in the genera Acanthoica and possibly Rhabdosphaera, can form combination coccospheres with holococcoliths (Cros et al. 2000 and Figs. 18B-D and 114).

Acanthoica acanthifera
The body coccoliths have a conical to somewhat sacculiform protrusion, which is slightly distally flattened and slightly compressed along its long sides; radial laths are somewhat tilted and separated by very narrow openings. Body coccoliths of this species are more robust but smaller than in other Acanthoica species. The spines of pole rhabdoliths are more robust than those of other Acanthoica pole rhabdoliths.
In the course of the present study some specimens have been found with the characteristics of this species (Figs. 16A, B) but other specimens have less tilted radial laths and a less sacculiform and flattened protrusion, suggesting that some transitional forms between this species and A. quattrospina may occur. More work is necessary to clarify this point.
Acanthoica quattrospina, the most common of all the Acanthoica species, differs from A. acanthifera in having the body rhabdoliths with a lower central protrusion, and not clearly tilted laths separated by wider openings. However, the observation of morphological variability in specimens of A. acanthifera (see A. acanthifera description) leads to think that more material has to be examined to ascertain if A. acanthifera is a real species or just a variety of the highly variable A. quattrospina. It is well known that the position of the spines is highly variable in this species (Kleijne, 1992) and the specimen figured in Fig. 17B is perhaps typical, with one long and three short spines at one pole and two long spines with laterally flattened bases at the other pole. The disposition figured in Fig. 17C with all the spines at one pole was originally described by Lohmann (1903) as Acanthoica coronata (more information is given in the revision of Kleijne, 1992).
The coccospheres possess between 45 and 105, including polar spines.
Body coccoliths are calyptroliths with a flat basal ring of well packed crystallites and a steeply tapered central protrusion tipped by one crystallite; usually these coccoliths present a few euhedral crystallites on the distal side forming the distal tip. Circum-flagellar calyptroliths are notably higher than body calyptroliths and are tipped by a thin and acute protrusion.

Algirosphaera robusta
Body rhabdoliths have a globular distal shape due to the large central area protrusion which usually obscures, in distal view, the rim and the radial laths; the proximal side of the hollow protrusion is covered by a layer of randomly arranged elements; three flattened and variably shaped circum-flagellar rhabdoliths are present which are higher than the body coccoliths and slightly undulated.
The morphology of the rhabdoliths of this species is highly variable, even on the same specimen. A detailed description of the rhabdoliths is given in Kleijne (1992).
Genus Anacanthoica Deflandre, 1952 Monothecate coccosphere with only one type of coccoliths with a conical central protrusion.
The coccoliths have a wide rim, a ring of radial laths and a wide blunt ended protrusion.

Cyrtosphaera aculeata
The coccoliths have the rim somewhat bent upwards and showing a well developed inner rim cycle (Kleijne, 1992), which is homologous to the external connecting ring in the genus Syracosphaera. The radial laths have a length/width ratio of around 3. The conical and relatively low protrusion has a well formed lamellar ring of dextrally arranged wide lamellae at its base, followed by some narrow and somewhat irregularly arranged needleshaped elements, and a blunt distal end which is tipped by a small papilla of cuneate elements.
Cyrtosphaera cucullata (Lecal-Schlauder, 1951) Kleijne, 1992 (Figs. 21A, B) Acantoïca cucullata, Lecal-Schlauder, 1951, p. 269-270, figs. 6a-d. Cyrtosphaera cucullata (Lecal-Schlauder, 1951) Kleijne, 1992. Coccoliths have a bowler hat shape due to the large central protrusion; the rim and the radial laths form a flat area surrounding the protrusion like the brim of a hat. The protrusion starts with a ring of very short laths at its base which are perpendicular and appear intercalated with the laths of the radial cycle, followed by elements of the lamellar cycle which become needle-shaped and are separated distally by small openings, and is tipped by a small papilla constructed of cuneate elements.
The dimensions of the three coccospheres as well as the long axis of the coccoliths measured in the present study are closer to those given by Lecal-Schlauder (1951) for Mediterranean specimens from the North Africa area than the larger North Atlantic specimens reported by Kleijne (1992). Too few specimens are available to determine if this is a systematic trend, but if so, differences of water temperature may be responsible.
Coccospheres possess from 45 to 70 rhabdoliths each of which has from 42 to 48 laths.
Genus Discosphaera Haeckel, 1894 Monothecate coccosphere with only one type of coccoliths which have a characteristic trumpet-like central structure, and so have been termed salpingiform rhabdoliths.
The central process of coccoliths of Palusphaera sp. 1 differs from that of P. vandelii in being thicker, especially in the middle part, and in being constructed by strong, thick elements. Further study is required to ascertain if this Palusphaera is another species or merely a variety, as is the case in Rhabdosphaera clavigera, which can show rhabdoliths with a thick spine (variety clavigera) or a thin spine (variety stylifera).

Rhabdosphaera clavigera
The shape of the process varies between claviform (characteristic for specimens originally described as R. clavigera) and styliform (characteristic for specimens originally described as R. stylifera) (Fig. 23A). The latter shape, with small "wings" of laterally extending elements ( Fig. 23B) instead of a straight end, was denominated R. stylifera var. capitellifera in Kamptner, 1937, p. 313, pl. 17, figs. 43-45. Nowadays, the process shape is considered characteristic of individual rhabdoliths (Kleijne, 1992) and not of entire rhabdospheres and hence it seems better to distinguish the coccospheres as "formae" rather than varieties clavigera and stylifera.
R. clavigera formae stylifera and particularly the formae capitellifera (with wings) are the most common in NW Mediterranean waters.
A coccosphere belonging to Sphaerocalyptra quadridentata half surrounded by part of a collapsed coccosphere of R. clavigera ( Fig. 114A) was found in the Barcelona offshore station T1, from the workshop named "Picasso" (July, 1998). In the station T5 of the same Picasso workshop, a disintegrated coccosphere of S. quadridentata was found next to several exothecal coccoliths of R. clavigera that appears a random product (Fig. 114B). Nevertheless, Kamptner (1941) noticed that S. quadridentata is combining with Algirosphaera robusta. These data appear, at the moment, inconsistent and so it is wise to think that more data is necessary to clarify the life-cycle of these coccolithophores.
Family SYRACOSPHAERACEAE (Lohmann, 1902) Lemmermann, 1903 This family groups genera which bear muroliths with a radial lath cycle, the caneoliths, but they can possess planoliths and/or modified derivatives on the same coccosphere. Most genera have a very high architectonic complexity (e.g. they can show either dimorphism, polymorphism or varimorphism associated sometimes with dithecatism or even possess large modified coccoliths as real appendages). Some of the representatives of this family in the genera Syracosphaera and Coronosphaera, show combination coccospheres with holococcoliths (Cros et al. 2000).
The family Syracosphaeraceae is the most diverse within the extant coccolithophores (Jordan and Kleijne, 1994) but has few fossil representatives (Perch-Nielsen, 1985) due to the small sized coccoliths with low preservation potential (Young, 1998).

Genera with appendages
Genus Calciopappus Gaarder et Ramsfjell 1954emend. Manton et Oates, 1983 Coccospheres with at least three kinds of coccoliths: the body caneoliths without flanges, an apical ring of whorl coccoliths and, attached distally to the whorl coccoliths, another ring of very modified spine-like coccoliths. These characteristic spines have a split base with a horseshoe-like end. This genus contains two recognized species, C. caudatus and C. rigidus, which are differentiated in electron microscopy studies by their coccoliths. C. caudatus has oblong caneoliths with central laths running somewhat obliquely to the sides, whilst C. rigidus has narrowly elliptical caneoliths with a developed wall. C. caudatus is a species typical of subpolar waters (Okada and Honjo, 1973;Okada and McIntyre, 1979) found particularly in shallow waters (Samtleben and Schröder, 1992;Samtleben et al., 1995) whilst C. rigidus is a species described from the subtropical North Atlantic (Heimdal and Gaarder, 1981), possibly related to subtropical to tropical waters and particularly to nutrient-enriched environments (Kleijne, 1993). Heimdal, 1981, in Heimdal andGaarder, 1981 (Figs. 24A, B) Coccosphere stiff, slender, cone-shaped; this species is described as having tetramorphic coccoliths Gaarder, 1981, Kleijne, 1993) but in the studied specimens the central apical caneolith with spine described in the diagnosis of the species was not observed, and only three different kinds of coccoliths have been seen. The body coccoliths are narrowly elliptical and are arranged in co-axial rings with the long axis parallel to the long axis of coccosphere and having most of the laths arranged at approximately right angles to the side of the caneolith; they have a high wall. Surrounding the flagellar opening the coccosphere has a whorl of subcircular, overlapping planoliths with the central opening partially filled by flat bands, and each with finger-like projections towards the centre of the whorl. A ring of spine-like appendages surround the whorl planoliths.

Calciopappus sp. 1 (very small) (Figs. 24C, D)
Small and weekly calcified Calciopappus. Small coccosphere with delicate caneoliths which have only the rim well calcified; the whorl planoliths have two finger like spines, one directed towards the coccosphere and the other, approximately at 90º forming a tangential anticlockwise pattern on the coccosphere in distal view; the appendages are short and thin.

Michaelsarsia elegans
M. elegans differs from M. adriaticus (formerly Halopappus adriaticus) in having stronger body caneoliths with a wider and thicker central structure, circum-flagellar caneoliths having a solid instead of centrally opened process, ring-shaped coccoliths with wider central opening and wider link coccoliths with a broad central opening.
O. hydroideus mainly differs from O. formosus in having narrower osteoliths which are constricted centrally having a higher length/width ratio (around 6 compared to around 3).

Coronosphaera binodata
The most characteristic feature of this species is the pair of pointed knobs in the central structure of the body caneoliths.
The coccosphere has 40 to 75 body caneoliths and around 6 circum-flagellar caneoliths with spines.
This genus was erected to contain only one species (G. corolla), which was first placed inside the genus Syracosphaera and subsequently in Umbellosphaera.
This species was erected as Syracolithus corolla, with Syracolithus being a subgenus of Syracosphaera by Lecal (1965a). Later, Gaarder, in Heimdal and Gaarder (1981), in view of the high degree of size variation in the coccoliths and especially with regard to the development of the wall, included this species in the genus Umbellosphaera Paasche. Kleijne (1993) introduced a new genus, Gaarderia, to include this controversial species possessing umbelloliths and caneoliths. However, the exothecal and endothecal coccoliths are very similar, and more closely resemble caneoliths than umbelloliths; moreover, in the present study, it is clearly demonstrated that members of the genus Syracosphaera can bear caneoliths as exothecal coccoliths. In view of this evidence, Gaarderia corolla could be placed back in the genus Syracosphaera. Nevertheless it may be convenient to maintain, at present, the genus Gaarderia to contain this species with unusual exothecal and endothecal coccoliths. Coccosphere with (25-) 35-45 (-60) body caneoliths and 6 to 18 exothecal coccoliths.
Genus Syracosphaera Lohmann, 1902 Coccospheres usually dithecate. Endothecal coccoliths are caneoliths with one, two or three flanges; dimorphism is frequent, with apical spine-bearing coccoliths, and sometimes also differentiated antapical coccoliths or even varimorphic body coccoliths. Exothecal coccoliths usually differ from endothecal coccoliths and can be planoliths or muroliths, but, as proven in the present study, may sometimes be caneoliths with a very similar structure to endothecal coccoliths; the exothecal coccoliths can cover totally or partially the coccosphere or, in some species, may only be present around the apical area (as deviating coccoliths). Representatives of this genus present hetero-holococcolithophore combination coccospheres (Cros et al. 2000b).
This complex genus contributes significantly to the high diversity of the extant coccolithophores; it contains numerous species, several of which (mainly small sized species) do not yet have an official name or diagnosis.
Morphologically, a caneolith, which is a type of murolith, is constituted by the rim and the central area. The rim consists of the wall and flanges (proximal, mid-wall and distal) (Fig. 7). The central area contains laths, a connecting external ring and a connecting central structure (Fig. 8).
The connecting external ring morphologically belongs to the central area, but structurally the elements are a continuation of the rim elements and it is homologous to the "internal rim" described by Kleijne (1992) in the family Rhabdosphaeraceae. This group was divided into three genera (Syracosphaera "sensu stricto", Caneosphaera and Coronosphaera) by Gaarder and Heimdal (1977). The purpose was to group the species as follows: 1) double-layered case, Syracosphaera "sensu stricto", 2) single layer (but may possess deviating coccoliths) with complete caneoliths Caneosphaera, and 3) one layer of caneoliths with extremely narrow proximal rim and a rather complex wall, Coronosphaera. Other authors defined the genus Syracosphaera more widely in the morphological sense (Okada and McIntyre, 1977) and considered the proposed classification of Gaarder and Heimdal unpractical for stratigraphic purposes and also when working with actual specimens, since the exothecal coc-coliths are not always present in the dithecate species and isolated caneoliths are often difficult to identify (Janin, 1987).
At present, the genus Syracosphaera can be considered as a group of species of widely variable morphology, but related by the possession of caneoliths (having one, two or three flanges), with the endotheca having monomorphic, dimorphic or varimorphic coccoliths, with or without exothecal coccoliths, but always lacking the kind of highly specialised polar coccoliths that are found in Michaelsarsia and other syracosphaerid genera (Jordan and Young, 1990). In recent taxonomical work (Jordan, 1991;Kleijne 1993, Jordan and Kleijne 1994, Jordan and Green, 1994, Young and Bown, 1997b) the genera Caneosphaera and Deutschlandia are eliminated and their species placed back in Syracosphaera. In a near future the genus Gaarderia may also be placed back into Syracosphaera (see explanations in Gaarderia text).
From the study of the variability of the exothecal coccoliths in the Syracosphaera genus (Cros, 2000) groups of species which share common characters have been distinguished; these groupings are useful for classification purposes and may even help to understand phylogenetic and ecological relationships. Here, following Cros, 2000, we classify the Syracosphaera species according to their exothecal coccoliths type.
All these Syracosphaera species have endothecal caneoliths with proximal and distal flanges.

Species with complex undulating exothecal coccoliths
Exothecal coccoliths only around the flagellar area. The endotheca presents differentiated apical caneoliths with four-ended spines and, usually, one or two caneoliths with a spine in antapical position. Knappertsbusch, 1993 (Figs. 30A-D) Syracosphaera marginaporata Knappertsbusch, 1993, p. Kleijne, 1993, p. 258-259, pl. 5, fig. 6. Coccosphere dithecate, with dimorphic endothecal caneoliths. The body caneoliths are highly variable in size and appear smooth due to the central area laths which seem to be fused together except along the margin, where a row of characteristic pore-like gaps occurs between the elements, next to the smooth distal flange; the number of pores is very variable (14 to 24). Circum-flagellar caneoliths are considerably smaller than ordinary caneoliths, have clear radial laths in the central area and bear a long rod-shaped process (about 1 µm length) tipped by four endings; usually they lack the distal flange, possibly because it is easily broken. The exothecal coccoliths, observed only around the apical pole, are irregularly-shaped with petaloid protrusions; they are defined in the present study as complex undulating coccoliths.

Syracosphaera marginaporata
The smooth appearance of the caneoliths and the row of gaps between the central area and the distal flange is characteristic of this species. We agree with Kleijne (1993) about the resemblance of this species to Syracosphaera ossa. Both species have a smooth distal flange, a high degree of size variability in body caneoliths, small circumflagelar caneoliths with a four pointed spine and similar shaped exothecal coccoliths. S. marginaporata differs, however, from S. ossa in having body caneoliths with a flat central area and no central structure, in not possessing circum-flagellar caneoliths with flattened spines and in having smaller coccoliths and coccospheres than S. ossa.
Dimensions. Coccosphere length 6-9 µm; body caneoliths length (1.7-) 2.3-2.7 (-3.4) µm; circumflagellar caneolith spine length ca. 1.5 µm; complex undulated exothecal coccolith diameter ca. 2.5 µm. ( Coccosphere dithecate with dimorphic endothecal coccoliths. The variable sized body caneoliths have a wide and smooth distal flange and may or may not possess a central structure, which can be very variable; it is noteworthy that near the apical and antapical poles the central structure typically becomes smaller or is absent. The circumflagellar caneoliths have a broad process characteristically extended in the direction of the major axis (Figs. 32A, C, D;and Lecal, 1965a, pl. 2 fig. 8). A caneolith with a short spine is usually present at the antapical pole. The exothecal coccoliths are smooth, complex and undulating and in the central part have two parenthesis-like openings bordering the ends of the ellipse; in proximal view one or two small nodes are present in the central part.

Syracosphaera ossa
S. ossa is a species closely related morphologically to S. molischii, but differs in having a smooth distal flange on the body caneoliths and smooth distal side to the exothecal coccoliths rather than being corrugated; moreover the circumflagellar caneoliths of S. ossa are characteristically broader and more laterally flattened than in S. molischii.

Species with simple undulating exothecal coccoliths
The exothecal coccoliths are, usually, in one area of the coccosphere. The endotheca presents body caneoliths with proximal and distal flanges and has no differentiated caneoliths with spine. Dithecate coccosphere (Cros, 2000) with monomorphic endothecal coccoliths. The body caneoliths have a narrow distal flange and the central area has characteristic perpendicular nodules/rods of variable size on the laths. The nodules of some specimens are positioned irregularly, but in others the nodules/rods are arranged very regularly; the coccoliths with a more regular rod distribution are typically smaller and more irregular in shape than the specimens in which the nodules are irregularly arranged. It could be useful to express such differences in the nomenclature. The exothecal coccoliths are simple undulating coccoliths with the ends bent upwards, giving a distally concave aspect.
Coccoliths of this species have nodules/rods in the central area like Syracosphaera epigrosa Okada et McIntyre 1977, but the distal flange is narrower and flaring (rather than wide, smooth and very flat), and no dimorphism of endothecal caneoliths is shown. Kleijne (1993) relates this species to Syracosphaera epigrosa Okada et McIntyre 1977 and to Syracosphaera sp. II cf. epigrosa Kleijne, 1993. She reports that the morphology of the caneoliths of Syracosphaera sp. I cf. epigrosa is intermediate between that of S. epigrosa, with their wider distal flange and highly variable pattern of nodules, and that of Syracosphaera sp. II cf. epigrosa, with a narrow distal flange and no nodules. The presence or absence of dimorphic endothecal coccoliths between S. epigrosa and Syracosphaera sp. I cf. epigrosa and the very different aspect of the central processes in the circum-flagellar caneoliths between S. epigrosa and Syracosphaera sp. II cf. epigrosa suggests that these three taxa are essentially different. So, the three taxa should be considered different species.
Syracosphaera species having disc-like exothecal coccoliths, which are planoliths. All these species have caneoliths without either distal or mid-wall flanges.
The heterococcolith coccosphere has body caneoliths with a short and thick wall with neither a distal nor a mid-wall flange; the laths of the central area raise up in the centre forming a structure which resembles a sloping tiled roof; these body caneoliths do not have complete bilateral symmetry since the central ridge formed by the union of the laths is slightly warped and shows some polarity at the two ends. The circum-flagellar caneoliths have a small central nodular spine. The exothecal oval coccoliths have a broad rim composed of similar elements, a ring of very short elements that connect the rim with the central part, the latter being covered by 12 to 14 plates which are triangular at the extremes of the coccolith ellipse and otherwise quadrate ( Fig. 36B and Kleijne, 1991, pl. 20 fig. 6); this solid central part is slightly convex in distal view.
Dimensions. Holococcolith coccosphere diameter 5.5-7.5 µm; body holococcoliths length (0.9-) 1.1-1.3 (-1.5) µm. Coccosphere dithecate with dimorphic endothecal caneoliths. The body caneoliths are very small with a very low wall and narrow proximal flange; the flat central area has no central structure and the laths are wider towards the coccolith wall, the inner end typically not being arranged radially. Circumflagellar caneoliths have laths oriented anticlockwise and a blunt low spine as a central structure. Anticlockwise precession of laths is very characteristic of both, body and circumflagellar caneoliths. Exothecal coccoliths are small, oval, disc-like coccoliths.
The body caneoliths of this species resemble the caneoliths of Syracosphaera sp. type B Kleijne (1993) p. 241 pl. 6 figs. 2-3, but the exothecal coccoliths do not have an indented periphery as the coccoliths figured in pl. 6 fig. 3 of Kleijne, 1993; moreover the coccosphere as well as the caneoliths of the S. sp. type B appear larger than S. sp. (aff. S. nana). The three coccospheres studied consist of 32, 40 and 40 body caneoliths; 1 to 5 circum-flagellar caneoliths with spine; some exothecal coccoliths on only one collapsed coccosphere.
The coccosphere is dithecate with dimorphic endothecal caneoliths. The body caneoliths have neither distal nor mid-wall flanges and posses a very thick and short double layered wall; central area with around 25 (from 23 to 28) laths which fuse in a broad central part and slightly climb into the inner wall. The circumflagellar caneoliths have a high, thick single layered wall and possess a short and thick rod-shaped central structure with rounded end. The irregular, subcircular exothecal coccoliths are solid, compact, with well developed and stratified layers on the distal side (somewhat resembling a fish otolith).
The caneoliths of this Syracosphaera sp. have double layered body caneoliths resembling the caneoliths of S. bannockii but having a rather broad central part instead a more or less elongated low mound; however the exothecal coccoliths have a completely different morphology showing a characteristic stratified aspect in this Syracosphaera sp. The specimens figured by Okada and McIntyre (1977) pp. 24-25, pl. 8 figs. 7-8 as Syracosphaera nana (Kamptner), by Heimdal and Gaarder (1981) p. 60, pl. 8, figs. 42a-b as S. cf. nana (Kamptner) Okada and McIntyre and Syracosphaera sp. type J Kleijne, 1993, p. 244, pl. 5 fig. 3 all resemble this Syracosphaera sp, but in the descriptions from these authors there is not mention of the double layered wall and the images do not show this structure; in addition the coccoliths of these quoted specimens are elliptical and not subcircular as in the specimen figured by Okada and McIntyre (1977) pl. 8 fig. 9 and the present Syracosphaera sp. Two different, but very close taxa may exist: the present S. sp. and S. sp. type J of Kleijne (1993).

Syracosphaera bannockii
A combination coccosphere showing coccoliths of both, Syracosphaera bannockii and the formerly Corisphaera sp. type A is figured in Figs Coccosphere usually ovoid; dithecate with dimorphic endothecal caneoliths. Body caneoliths with low and thick wall and neither mid-wall nor distal flange; central structure from nearly flat to a slightly elongated mound, radial laths resting directly on the wall without external connecting ring. Circumflagellar coccoliths with a pointed spine which usually appears slightly bent. Exothecal coccoliths are asymmetrical disc-like coccoliths, broadly elliptical with a pointed extended rim.
This Syracosphaera strongly resembles Syracosphaera sp. type K Kleijne, 1993, p. 244, pl. 6 fig. 11, it differs mainly in having exothecal coccoliths without thickened or stratified parts as shown in the coccoliths of Syracosphaera sp. type K.
N.B. These two coccolith morphotypes (solid and perforated) are sufficiently distinctive to be worth separating, since they may be ecologically distinct. However their co-occurrence on single coccosphere makes it unlikely they are genotypes. Cros et al. 2000. (Figs. 42A-D) Syracosphaera delicata Cros et al., 2000, p. 29-32, pl Coccosphere dithecate with dimorphic endothe-cal caneoliths. The body caneoliths have a delicate, lightly calcified appearance, and are often bent or deformed; they have a narrow proximal flange and neither distal nor mid-wall flanges; the wall is low and smooth and its elements are easily distinguished; the central area has 19 to 26 laths which join forming a flat and smooth central part. The circum-flagellar caneoliths have a very short and thin central protrusion. The exothecal coccoliths are asymmetrical disc-like planoliths; they are formed of three rings of elements: a variably wide rim of juxtaposed elements, of which one is larger and laterally protruding giving the coccolith its pointed extension; a radial ring of around 20 short laths, separated by wide slits, and a central part of around 12 elements showing clockwise imbrication/obliquity in distal view; the central part and radial cycle are subcircular and flat but the rim is more elliptical to rhomboid in outline and bears a thin, almost straight, characteristic distal ridge. These exothecal coccoliths are often positioned in an imbricate arrangement, forming a ribbon. A disintegrated specimen, which is not a conclusive combination coccosphere, with heterococcoliths of this Syracosphaera and holococcoliths of Corisphaera sp. type B of Kleijne (1991) was found through this study (Fig. 113C).

Syracosphaera delicata
The coccosphere resembles the images and description of Pontosphaera nana by Halldal and Markali (1955), particularly with respect to the endothecal caneoliths; both have no distal flange, a wide and flat central area and a fragile appearance, but Syracosphaera delicata has caneoliths with lower walls and narrower and shorter slits between laths; the exothecal coccoliths also closely resemble each other, but Halldal and Markali's exothecal coccoliths are more elongated and have shorter and more numerous laths in the radial ring (22-23 compared to 20 in S. delicata). Syracosphaera delicata also resembles S. orbiculus Okada and McIntyre (1977), both in terms of the morphology of the exothecal coccoliths and the large flat central structure of the caneoliths; it differs from this species, however, in having smaller caneoliths with a more fragile appearance, in having circum-flagellar coccoliths with a very small spine (around 0.3 µm compared to 1 µm described by Okada and McIntyre, 1977) and smaller exothecal coccoliths with a narrower rim.
It is remarkable that the coccosphere of this species is small, and appears delicate. The caneoliths have a characteristic smooth and fragile aspect and the circum-flagellar caneolith possesses a very thin, short and sharp spine. The exothecal coccoliths have a characteristic longitudinal ridge on a quarter of the rim.
Coccosphere subspherical to ovoid; dithecate with dimorphic endothecal caneoliths. Body caneoliths with a thick and smooth wall and neither distal nor mid-wall flanges; central area with no connecting external ring, 25 to 26 short and irregularly widened laths, and a broad, flat and smooth internal connecting structure. Circum-flagellar caneoliths with a medium sized spine. The exothecal coccoliths are asymmetrical disc-like planoliths with a wide rim, very short radial laths and the central area filled with elements showing clockwise obliquity in distal view.
The caneoliths of this species are reminiscent of S. orbiculus caneoliths, but differ from them in not having a connecting external ring which is very clear in the caneoliths figured in Okada and McIntyre (1977) pl. 9 fig. 6, and in possessing smaller and more elliptical exothecal coccoliths.
Coccosphere spherical; dithecate with dimorphic endothecal coccoliths. Body caneoliths with a thin and smooth wall and neither distal, nor mid-wall, flanges; central area with a well developed connect-ing external ring, a flat, elongated internal connecting structure and 18 to 26 laths (characteristically at each end of the caneolith, a short lath which does not extend to the central structure but joins with the neighbouring lath is observed). Circum-flagellar caneoliths with a long and somewhat bent spine. The exothecal asymmetrical disc-like coccoliths have two longitudinal segments of the rim sides conspicuously bent.
The body caneoliths and the circum-flagellar spine-bearing caneoliths of these specimens strongly resemble those of S. orbiculus Okada and McIntyre, but the shape of the exothecal coccoliths differs between the two species.
This taxon was also found in North Atlantic waters (M. Cachão and A. Oliveira, personal communication, 1999).

Species with thin (sub-)circular exothecal coccoliths
The endotheca has no differentiated circum-flagellar caneoliths. Lecal-Schlauder, 1951 (Fig. 44) Syracosphaera lamina Lecal-Schlauder, 1951, pp. 286-287, figs. 23-24;Borsetti and Cati 1976, p. 215 Coccospheres very variable in shape; may possess exothecal coccoliths but no differentiated circum-flagellar endothecal coccoliths. Endothecal caneoliths have a high wall with an undulated top, and a narrow proximal flange; the central area has 30 to 36 laths which become narrower towards the centre of the coccolith and a very characteristic elongate keel-like central structure which connects the laths on the distal face; the proximal side of the caneoliths has two conspicuous straight and low central longitudinal ridges, overlapping along one third of their length (Fig. 44D) and connecting the laths; the laths from the ends of the caneolith join one another, forming ear-like structures. Exothecal coccoliths are thin, subcircular, disc-like coccoliths with serrated edges; they are composed of three parts: a wide rim of wide elements, a radial cycle of narrow elements and a solid central part which appears to consist of two plates.

Syracosphaera lamina
This species closely resembles Syracosphaera tumularis; it differs from the latter in having caneoliths with narrowly elliptical shape instead of a normally elliptical outline, in possessing centrally narrowing laths instead of straight laths and in having a high keel-like central structure which is not present in S. tumularis.
The coccospheres consist of 80 to 120 caneoliths, sometimes with a few exothecal coccoliths.
Dimensions. Coccosphere length 20-40 µm; body caneolith length (3.1-) 3.4-3.8 (-4.0) µm; exothecal coccolith diameter ca. 3.5 µm. Sánchez-Suárez, 1990 ( Coccosphere dithecate (Cros, 2000) with monomorphic endothecal caneoliths. The caneoliths have a high and thin wall and a central area with 33 to 37 straight laths that connect the wall with the central structure, which is an elongated mound constructed by irregular transverse elements (some of these elements are a narrow continuation of the laths). The exothecal coccoliths are broad, thin, subcircular and lamina-like with a central structure consisting of two plates resembling that of S. nodosa. The caneoliths of this species differ from those of S. lamina in having a relatively low, more or less complex central structure, instead of possessing an elongated conspicuous keel-like central structure, in having a lower length/width ratio, and a thinner wall; in addition the exothecal coccoliths are more rounded and have more complex polygonal central plates.

Syracosphaera tumularis
This species was described by Sánchez-Suárez (1990) as having dimorphic endothecal coccoliths and with dithecatism not observed, but in the comments he points out that the differentiated circumflagellar caneoliths have only been observed under light microscopy; Kleijne (1993) did not observe either dithecatism or dimorphic coccoliths. From the observations in the present study, it can be concluded that this species is dithecate, with only one kind of endothecal coccolith.
The coccospheres studied consisted of 36, 48, 50 and 58 body caneoliths and indeterminate numbers of exothecal caneoliths (more than 10-15 in several studied coccospheres; they are very loosely attached to the coccosphere and in consequence they are easily lost).
The caneoliths of Syracosphaera sp. type L of Kleijne differ from the caneoliths of S. nodosa in having straight rather than irregular-undulating walls and in having irregular compared with regular laths, moreover the central mound is lower and more irregularly shaped; the exothecal coccoliths of both species are easily differentiated, since Syracosphaera sp. type L has no distinguishable radial laths.

Species with wheel-like exothecal coccoliths
Exothecal coccoliths are planoliths with a ring of conspicuous radial laths. The endotheca has differ-entiated circum-flagellar caneoliths with robust spines. Kamptner, 1941 (Fig. 46) Syracosphaera nodosa Kamptner, 1941, pp. 84-85, 104, pl. 7 figs. 73-76;Nishida, 1979 Coccosphere dithecate with dimorphic endothecal caneoliths. Body caneoliths, without either distal or mid-wall flanges, have characteristic vertical ribs on the outer surface of the wall; the central area is formed by a solid external connecting ring and the laths which meet in a connecting elongated central structure. The circum-flagellar caneoliths possess a strong spine. Exothecal coccoliths are characteristic wheel-like coccoliths composed of three different parts: an angular central part formed of two rectangular plates which are easily distinguished in distal view, a broad rim composed of similar elements and a radial cycle of laths (from 19 to 23) which overlap on the distal face of the rim.

Syracosphaera nodosa
A group of coccoliths which appeared to be a mixed collapsed coccosphere of S. nodosa with Helladosphaera cornifera was found (Fig. 113D).
Dimensions. Coccosphere long axis (6.0-) 6.5-7.5 (-9.5) µm; body caneoliths length (1.7-) 2.3-2.5 (-2.6) µm; circum-flagellar caneolith spine height 1.3 µm; exothecal coccolith diameter 2.5 µm. Dithecate coccosphere with dimorphic endothecal coccoliths. Body caneoliths with a distally flared wall which is wavy ended and has vertical ribs on the outer surface; they possess a well developed proximal flange, but neither distal nor mid-wall flanges; the central area has 24 to 30 slender radial laths and an elongated mound as a central connecting structure. The circum-flagellar caneoliths possess a slender process. Exothecal wheel-like coccoliths resemble those of S. nodosa. Syracosphaera sp. aff. S. nodosa strongly resembles S. nodosa. Caneoliths of Syracosphaera sp. resemble caneoliths of S. nodosa in having a distally widening wall with characteristic vertical ribs on the outer surface and in having an elongated central mound, but differ in having a higher wall (0.6 µm high compared to 0.3 µm in S. nodosa), in connecting the lamellar elements of the central area directly to the wall instead of ending at the external connecting ring and in having more numerous and thinner laths. The spine of the circum-flagellar caneoliths is thinner and shorter than in S. nodosa. Exothecal wheel-like coccoliths have the same structure as those of S. nodosa, but are bigger, with a wider rim and central area and in having more numerous radial laths (24-29 compared to 19-23 in S. nodosa); moreover the rim of these exothecal coccoliths characteristically has narrow slits between the elements, which are not seen in S. nodosa.
In the one specimen where it was possible to count, 28 body caneoliths and only 5 spine-bearing circum-flagellar caneoliths were present; more than 50 exothecal coccoliths can be present.

Syracosphaera rotula
Coccosphere dithecate; no differentiated circumflagellar endothecal coccoliths observed. Endothecal caneoliths with proximal and distal flanges, a very thin wall and no central structure. Exothecal coccoliths circular with a rim with its end bent through the proximal side, an intermediate ring of around 25 sinistrally radiating long, flaring laths, and a central part composed of two plates. Two specimens recorded from winter samples (Hivern-99 cruise) The exothecal coccoliths of Syracosphaera rotula resemble those of S. nodosa, differing mainly in having longer laths, which are not in the same plane as the central structure, and in having a narrower and bent rim. The endothecal coccoliths are, however, very different.

Syracosphaera species with vaulted exothecal coccoliths
Exothecal coccoliths appear as inverted muroliths. The endotheca has body caneoliths with proximal, mid-wall and distal flanges, and presents differentiated apical caneoliths with bifurcated spines. Kamptner, 1941 (Fig. 49) Syracosphaera histrica Kamptner 1941  Coccosphere dithecate with dimorphic endothecal caneoliths. The body caneoliths have a rim with a low wall, narrow distal and proximal flanges and a beaded mid-wall flange; central area with a slightly convex floor consisting of about 30 laths directed and fused towards the centre where they form a short irregularly tipped spine. The circum-flagellar caneoliths have a long central spine with bifurcate endings. The exothecal coccoliths are very conspicuous vaulted coccoliths, with a narrow rim and an irregularly featured, slightly elevated central area which resembles a branching root system.
S. pulchra is the best known of the Syracosphaera species, possibly due to its relatively large size. The classical description was given by Lohmann, 1902, and the species was selected as type of the genus by Loeblich and Tappan (1963). Kamptner (1941, pl. 8, figs. 82-84) depicted S. pulchra cells with a double layer of coccoliths, a feature which he was the first to record (1939, p. 120). Gaarder and Heimdal (1977) showed that the proximal coccoliths are formed on a radially striped organic base-plate scale. A detailed study was provided by Inouye and Pienaar (1988) based on the examination under light and electron microscopes of cultured specimens.
Sediments as well as two samples of Mediterranean water contained some flower-shaped coccoliths with an extended wing or petal-like rim which seem related to S. pulchra, possibly representing malformed specimens of coccoliths of this species (Fig. 50B); such kind of S. pulchra coccoliths were previously observed by J.R Young in culture samples (personal communication).

Species having elliptical caneoliths with flanges as exothecal coccoliths
The endotheca has body caneoliths with proximal, mid-wall and distal flanges, and presents spine-bearing circum-flagellar caneoliths with robust spines.
Syracosphaera cf. dilatata Jordan, Kleijne et Heimdal, 1993 (Fig. 52) Heimdal, in Heimdal and Gaarder, 1981, p. 44, pl. 2, fig. 9a-b. Syracosphaera halldalii f. dilatata (Heimdal, in Heimdal and Gaarder, 1981) Jordan et Young, 1990;Kleijne 1993 p. 238, pl. 4 fig. 10. Syracosphaera dilatata Jordan, Kleijne et Heimdal, 1993, pp. 18, 20;Jordan and Green, 1994, pp. 156, 160, 161. Syracosphaera cf. S. dilatata Jordan Kleijne et Heimdal, 1993;in Cros, 2000, Plate 6, figs. 1 and 2. Coccosphere considered dithecate (Cros, 2000) with dimorphic endothecal caneoliths. The coccosphere has from 35 to 65 body caneoliths, around 5 circumflagellar spine-bearing caneoliths and from 12 to 30 (or may be more) exothecal caneoliths. The body caneoliths have a relatively narrow distal flange that expands obliquely outwards and has a corrugated surface with a radially ribbed appearance, with regular undulate endings along the rim; the outer part of the wall has a row of beads, not previously recorded, which can form a sort of mid-wall flange; the central area is constituted of 19 to 26 laths and has an elongate mound as a connecting central structure. The circum-flagellar caneoliths have a beaded row, mentioned before by other authors (Heimdal and Gaarder, 1981;Hallegraef, 1984), and a robust process that ends in four small peaks. The exothecal coccoliths are caneoliths very similar to the body coccoliths, but larger, with higher fragile walls that have an almost imperceptible external row of beads positioned where the flared distal flange starts; the distal flange is radially ribbed and appears fragile; the central area consists of 20-30 radially placed laths fused along a central line. These exothecal caneoliths resemble the coccoliths reported by Heimdal and Gaarder (1981) pl. 2 fig. 9 as Caneosphaera halldalii f. dilatata.
The exothecal caneoliths differ from the endothecal coccoliths in being larger but thinner, in having higher, more fragile walls with almost imperceptible beaded mid-wall flanges (compared with shorter and thicker walls with clear beaded mid-wall flanges) and in having a smaller central structure. The fragility of these exothecal caneoliths sometimes results in the wall and distal flange splitting off.
The Syracosphaera described here differs from the last reported Caneosphaera halldalii f. dilatata Heimdal by having stronger and slightly smaller body coccoliths with more marked nodules on their outside wall. The circumflagellar caneoliths have the same dimensions and show similar nodules on the external side of the wall as the specimens recorded by Heimdal and Gaarder (1981) and Hallegraef (1984). The similarity between the exothecal caneoliths of this Syracosphaera and the caneoliths illustrated in Heimdal and Gaarder (1981) pl. 2 fig. 9 as Caneosphaera halldalii f. dilatata, suggests that the coccoliths shown in Heimdal and Gaarder (1981) might be exothecal coccoliths of this species or that the present studied specimens might be a different variety of the S. dilatata described and figured by Heimdal and Gaarder (1981). Heimdal and Gaarder (1981) described this species as a variety of Caneosphaera halldalii f. halldalii Jordan and Young (1990) proposed that this species of Caneosphaera be transferred back to Syracosphaera as the reliability of the Caneosphaera generic description became doubtful (C. molischii possesses exothecal or deviating coccoliths and C. halldalii f. dilatata possesses circumflagellar coccoliths with bead-like knobs i.e. a kind of mid-wall flange). Finally, Jordan et al. (1993) elevated S. dilatata to species level, finding it significantly different from the type S. halldalii f. halldalii and in Jordan and Green (1994) this species is definitively validated as S. dilatata by reference to the published description and holotype negatives of Heimdal and Gaarder (1981). The recognition of dithecatism by Cros (2000) in this species strongly supports its separation from S. halldalii.
Dimensions. Coccosphere long axis (9-) (10-12) (-14) µm; body caneoliths length (2-) 2.3-2.5 (-2.7) µm, width 1.3-1.8 µm; circum-flagellar caneoliths diameter 1.5-2µm, spine length 1.5-2 µm; exothecal caneoliths length (2.3-) 2.7-2.9 (-3.1) µm, width 1.7-1.8 µm. Coccosphere dithecate (Cros, 2000) with dimorphic endothecal caneoliths. The body caneoliths have a proximal, a mid-wall, and a distal flange; the distal flange expands obliquely outwards, and has two concentric kinds of ribs, the inner wider than the outer (a feature that gives the impression that the distal flange bears two rows of nodules with the inner ones thicker and less numerous); the central area has 20 to 30 laths and an elongate convex central structure made of sub-vertical elements. The circum-flagellar caneoliths, with beaded mid-wall flanges, have a robust square-shaped process tipped by four small rounded nodes. Exothecal coccoliths are caneoliths very similar to the ordinary ones; they are larger but seem more fragile than the body caneoliths, have higher walls, lack a well developed external mid-wall flange but have a wider distal flange without the thick inner row of nodules that is noticeable in body caneoliths.
This species closely resembles S. cf. dilatata (see above) in general shape, in the morphology of circum-flagellar caneoliths and in the structure of exothecal caneoliths. The body caneoliths have a fold-like rather than a beaded mid-wall flange, however, as well as the presence of nodules on the inner part of the distal flange; moreover the exothecal caneoliths have a wider distal flange than in S. cf. dilatata.
Figs. 113A, B represent two associations of Syracosphaera sp. type D coccoliths with Homozygosphaera arethusae holococcoliths; but these associations could be a random product, as discussed in Cros et al. (2000).

Species having elliptical caneoliths, with nodes, as exothecal coccoliths
The endotheca has body caneoliths with neither distal nor mid-wall flanges, and presents spine-bearing caneoliths with bi-ended long spines around the flagellar area. Knappertsbusch, 1993, orthog. emend. Jordan et Green, 1994 Syracosphaera sp. type E, Kleijne (1993), p. 242, pl. 6, fig. 4. Syracosphaera noroiticus Knappertsbusch, 1993, p. 71-72, pl. 1 fig. 1-3 Coccosphere dithecate; endotheca presents polymorphic caneoliths. The body caneoliths have nei-ther distal nor mid-wall flanges; show smooth and thick walls and the laths extend up the internal sides of the wall. These caneoliths show a gradually polar varimorphism; the most apical body caneoliths have higher and thicker walls and central processes, characters which diminish toward the antapical pole where caneoliths have low and thin walls and no central process; the smallest caneoliths, at the antapical pole, have lath extensions protruding as thorns above the rim of the wall (Fig. 54B). These body coccoliths thus appear in three basic morphologies: a) near the apical pole they are robust with a thick and blunt central spine and show varimorphism; b) near the antapical pole they lack the central spine; c) at the antapical pole there are some small caneoliths with two lateral spines which are prolongations of the central laths. The circum-flagellar caneoliths possess a long central spine, forked at the end. The exothecal coccoliths are true elliptical caneoliths (Cros, 2000) with slender laths in the central area that extend marginally and seem to protrude out the wall forming nodes; these nodes form a beaded proximal flange, similar to S. prolongata exothecal coccoliths. The exothecal caneoliths have a thinner central protrusion and thinner walls than the similar-sized endothecal ones and have a cobweb pattern in the central area of the proximal side. The central spines of the body and exothecal caneoliths are constructed by characteristic vertical elements.
Syracosphaera sp. type G of Kleijne 1993 (Fig. 55) Syracosphaera sp. type G, Kleijne 1993, p.243, pl.6, figs. 6, 9. Coccosphere dithecate (Cros 2000); the endotheca has differentiated circum-flagellar caneoliths and varimorphic body caneoliths. Body coccoliths have a low wall with a characteristically incised upper margin and neither distal nor mid-wall flanges; the central area possesses 16 to 27 radial laths and a nodular, blunt central structure consisting of vertical elements; the central structure diminishes from the apical to antapical zone, being absent in the most antapical caneoliths. Circum-flagellar caneoliths have a long spine, forked at the tip. The exothecal coccoliths are caneoliths with a higher wall than the body caneoliths, the distal end of which is serrated, and have laths (25 to 28 radial laths) which protrude out of the wall forming small knobs around the coccolith, like a proximal flange.
Syracosphaera sp. type G is closely related to S. noroitica in both endothecal and exothecal coccolith structure, but differs from the latter in having smaller coccoliths with a thinner wall, fewer laths and a thicker nodular central protrusion. It closely resembles S. florida Sánchez-Suárez, 1990 and the Unidentified heterococcolithophorid "F", Heimdal and Gaarder 1981, p. 67, pl. 13, fig. 65, but the central spines of S. florida are thinner and those of "F" are thicker and extended along the long axis; moreover the wall of Syracosphaera sp. type G is very low and distally is characteristically different from that of the other related species.
The studied coccospheres were collapsed, consisting of more than 35 to around 60 body caneoliths; around 6 spine-bearing circum-flagellar caneoliths; and more than 4 exothecal caneoliths.

Syracosphaera prolongata
The coccosphere is dithecate with dimorphic endothecal caneoliths; it can be elongated (Throndsen, 1972, figs. 22-25) or can be from spherical to obpyriform (Fig. 56A). The body caneoliths have a low wall with three smooth flanges and a small rounded central node. The circum-flagellar caneoliths have a long spine, forked at the end. The exothecal coccoliths are sub-circular caneoliths; wider gaps are present between the laths than on the body coccoliths and near the centre the laths seem to join to form a hollow cone, whereas around the internal margin of the rim the laths protrude out of the wall forming a beaded proximal flange; the low wall has a very narrow distal flange. Both endothecal and exothecal caneoliths often show a characteristic thread-like pattern across the laths around the coccolith (Figs. 56B, D).
This species is structurally similar to S. pirus. According to Kleijne (1993) S. prolongata differs from S. pirus in having caneoliths with a smaller nodular protrusion and a larger number of radial laths in the central area, while also its exothecal coccoliths have a larger number of radial laths in the central area.
Dimensions. Coccosphere long axis ca. 10 µm (but in the literature it is described as reaching 70 µm: Throndsen, 1972, Okada andMcIntyre 1977); body caneoliths length (1.7-) 2.0-2.4 (-2.6) µm, with 25 to 32 laths; circum-flagellar caneolith spine length ca. 1.5 µm; exothecal caneolith diameter ca. 2.4 µm, with 28 to 36 laths. Gran ex Lohmann, 1913 sensu Heimdal andGaarder, 1981 (Figs. 57A, B) Syracosphaera prolongata Gran ex Lohmann, Heimdal and Gaarder, 1981, p. 60-62, pl. 10 figs. 48-50;in Winter and Siesser, 1994, p. 139 fig. 121 (Phot. from Knappertsbusch); Giraudeau and Bailey, 1995, Plate 5, figs. 2-3. The coccosphere is dithecate with dimorphic endothecal coccoliths; it can be elongated, slender cone-shaped or more or less pear-shaped. Body caneoliths have a thin wall with three smooth flanges; the central area has from 30 to 36 slightly vertically curved laths, resembling that of S. anthos caneoliths; the laths connect in the centre to form a low and twisted mound-like central structure. The circum-flagellar caneoliths have a long spine forked at the end. The exothecal coccoliths are circular caneoliths with 32-42 separate laths which join near the centre to form a hollow twisted mound; these laths protrude out of the wall as small nodes forming a beaded proximal flange; the low wall appears to have a very narrow distal flange; in the central area, some of these coccoliths have the remains of a thread-like structure crossing the laths around the coccolith. The exothecal caneoliths are bigger, but appear more fragile than the endothecal coccoliths.

Syracosphaera prolongata
The most characteristic feature of this species is the twisted central mound, present in body coccoliths as well as exothecal coccoliths; it differs from S. prolongata sensu Throndsen mainly in having larger caneoliths with this characteristic twisted mound central structure as opposed to a small rounded nodule.
The special characteristic of this species is the medial expansion of the laths. It differs from S. ossa in not having spine-bearing caneoliths around the flagellar area, in possessing more regularly shaped caneoliths and in not having a smooth distal flange as in S. ossa.

Syracosphaera halldalii Gaarder ex Jordan et
Green, 1994 (Fig. 58 Coccosphere monothecate with dimorphic coccoliths. Body caneoliths have a high and almost vertical wall with two flanges, the distal flange usually being wide and smooth; the central area has a longitudinal and very narrow central structure sometimes forming a low ridge . Circum-flagellar caneoliths very few in number, with a central spine, square in section. Three different morphologies can be distinguished in S. halldalii: a) the "ordinary form" (Plate 4 Fig. 4 in Kleijne, 1993) the coccoliths of which have a flat distal flange without protrusions, b) the "tooth-like form" (Figs. 58A, B) with a very wide and smooth distal flange that has tooth-like protrusions, and c) the "finger-like form" (Figs. 58C, D) with a relatively narrow distal shield, the surface of which is slightly ribbed by the edges of elements; this latter form is the former Syracosphaera protudens described by Okada and McIntyre (1977). In our opinion the "ordinary form" and the "tooth-like form" may be the same species (see in Fig. 58A a "tooth-like form" specimen having some coccoliths resembling those of the "ordinary form" figured in Gaarder and Heimdal, 1977, fig. 36), whereas the "finger-like form" (former S. protudens) is a different variety or even a different species, as Okada and McIntyre (1977) described. Further observations are required to clarify this taxonomic problem.
The classical description of a complete caneolith, given by Halldal and Markali (1954b), was based on thorough studies under the transmission electron microscope of a specimen identified as Syracosphaera mediterranea Lohmann. This name was, however, already employed for another species (see Coronosphaera mediterranea). As a consequence, Gaarder and Hasle (1971) proposed the new name of S. halldalii Gaarder for Halldal and Markali's specimen. Further studies on this species were carried out by Gaarder and Heimdal (1977) leading to a re-identification of Halldal and Markali's coccoliths with the new generic name of Caneosphaera. Jordan and Green (1994) validated the name of Syracosphaera halldalii with a latin diagnosis and redescribed the species on the basis of the observations made by Halldal and Markali (1954b) and Gaarder and Heimdal (1977) which included the S. protudens described by Okada and McIntyre (1977).
Order PRINSIALES Young et Bown, 1997 Monomorphic coccospheres with placoliths that usually have grill-like structures in the central area and straight and non-imbricate shield elements. Among the representatives of this order, Emiliania huxleyi and Gephyrocapsa oceanica are known to alternate with non coccolith-bearing phases.
Family NOËLAERHABDACEAE Jerkovic, 1970 emend. Young et Bown, 1997b Placoliths of the Reticulofenestra-type (Young, 1989): proximal and distal shields, two tube element cycles with opposite senses of imbrication and usually a central area structure. The members of this family differ from other coccolith bearing species in that they lack haptonema and produce unusual longchain lipids similar to those found in species of Isochrysis and Chrysotila (Marlowe et al., 1984;Jordan and Green, 1994), and in recent phylogenetic studies (Kawachi and Inouye, 1999;Fujiwara et al. 2001;Saez et al., in prep.) they appear to be related to Isochrysis galbana Parke emend. Green et Pienaar. Even authors who follow the classification of Parke and Green, in Parke and Dixon (1976) for the bulk of coccolithophores took this family out of the order Coccospherales, to place it in the order Isochrysidales (e.g. Kleijne, 1993;Jordan and Green, 1994).
Genus Emiliania Hay and Mohler in Hay et al., 1967 The placoliths have slits between all of the elements of the distal shield; these elements are Tshaped with interlocking ends at the margin. (Lohmann, 1902) Hay and Mohler in Hay et al., 1967. Fig. 59.
Observations in cultures (Klaveness, 1972;Green et al., 1996) have elucidated a complex E. huxleyi life-cycle with a dominant phase that produces non-motile heterococcolith bearing cells (Ccells), which sometimes give rise to non-motile naked cells (N-cells), and an alternate phase that produces motile non-calcifying cells with organic body scales (S -cells).
This species can be covered by several layers of placoliths which may show a high diversity in structure. This diversity has lead to recognition of distinct morphotypes, referred to as Types A, B, and C (Young and Westbroek, 1991) and E. huxleyi var. corona Okada and McIntyre (1977). Indeed, types A, B, and C have been considered as distinct taxonomic varieties, being called respectively E. huxleyi (Lohmann) (Medlin et al., 1996). Not all authors accept and follow this nomenclature.
The most abundant morphotype in the samples in this study was clearly Type A (Figs. 59A, B). Type C coccospheres (Fig. 59C) were found less frequently, but type B was not definitively identified and E. huxleyi var. corona was not found. However, in the studied samples other types of Emiliania huxleyi coccospheres, not previously described as existing morphotypes, were abundant and easily recognizable. These included a type with a non-calcified central area, with or even without an organic plate, a morphology related to type C, and an overcalcified type with the inner tube elements growing into the central area (Fig. 59D), which was frequently observed in waters deeper than 40 m. At present, it would be cautious not to separate these different E. huxleyi into morphotypes or varieties, and to delay any proposal of classification until a more complete study of this species in this area has been conducted.
Genus Gephyrocapsa Kamptner, 1943 The placoliths have a reticulate grid covering the proximal side of the central area and a characteristic bridge formed of two diametrically opposite extensions of inner tube elements.
Gephyrocapsa is a complex genus with considerable interspecific variability. Some authors (Samtleben, 1980) use size and bridge angle to distinguish between species or to relate the characteristics with environmental conditions (Bollmann, 1997). Thus, the taxonomy at the species level is still in a state of flux. Well established species such as G. protohuxleyi McIntyre or G. ornata Heimdal may represent different morphotypes of the species G. ericsonii McIntyre et Bé (Kleijne, 1993). In the present study, G. protohuxleyi is considered as a synonym of G. ericsonii because transitional forms have been found between them, but G. ornata, due to its singular characteristics, is presented provisionally as a different species, until more work is carried out on this subject. McIntyre et Bé, 1967 (Fig. 60) Gephyrocapsa ericsonii McIntyre and Bé 1967, p. 571, pl. 10, pl. 12, fig. b;Borsetti et Cati, 1979, p. 158, pl. 14, fig. 1 The placoliths are small (< 2.3 µm length) and have the bar at a low angle (around 15º) with the length (Samtleben, 1980). Gephyrocapsa ericsonii is the second most abundant coccolithophore in NW Mediterranean waters after Emiliania huxleyi.

Gephyrocapsa ericsonii
Considerable morphological variability was found in G. ericsonii and the specimens can be classified into three groups with more or less clear limits: ericsonii (without slits between distal shield elements, Fig. 60A), protohuxleyi (with slits between distal shield elements, Fig. 60B), and protohuxleyi-"with thorn" (with well developed slits and also a slender thorn that grows from the placolith inner tube, Fig. 60D). These groups may be different species or morphological variants along a continuous gradient; the presence of intergrades between protohuxleyi and protohuxleyi-"with thorn" (Fig. 60 C) may prove ecophenotypic rather than genotypic variation.

Gephyrocapsa muellerae
The placoliths are larger than those of G. ericsonii and have the bar forming a higher angle with the long axis than in G. ericsonii (Samtleben, 1980). Coccospheres possess between 14 and 24 coccoliths (5 coccospheres).
Genus Reticulofenestra Hay et al. 1966, emend. Gallagher 1989 Placoliths without slits between the distal shield elements or bridge; proximal side of the central area typically filled by a reticulate grid or a grill but may be filled by a more or less solid plate, or may appear open. (Okada et McIntyre, 1977) Biekart, 1989 var. parvula (Fig. 61D Placoliths small (1.5 -2 µm length) with central area filled by a reticulate grid; they differ from Gephyrocapsa ericsonii in not having a central bridge, and they differ from Emiliania huxleyi in not having slits between the distal shield elements.

Reticulofenestra parvula
Some specimens of Gephyrocapsa ericsonii from the NW Mediterranean have placoliths without a bridge (Cros 2001, pl. 40, figs. 2 and 3) which closely resemble the placoliths of R. parvula var. parvula. Similar specimens were figured by Heimdal and Gaarder (1981) pl. 4, figs. 20 a-b; Moreover, Okada and McIntyre (1977) point out the similarity between placoliths of G. ericsonii and R. parvula var. parvula. A very close relationship between these species is evident and indeed the possibility exists that R. parvula var. parvula consists in fact of specimens of G. ericsonii which lack the distal bar in all of their placoliths.
Order COCCOSPHAERALES Haeckel, 1894 emend. Young andBown, 1997 Monomorphic coccospheres with placoliths, usually without structures in the central area and with curved and overlapped shield elements. Alternations with holococcolith-bearing phases have been reported for two representatives of this order, Coccolithus and Calcidiscus.
Family CALCIDISCACEAE Young et Bown 1997b Placoliths have the rim structure characteristic of Calcidiscus: large distal shields with sutures that typically show levogyral curvature.
Genus Calcidiscus Kamptner, 1950 Placoliths subcircular with the central area closed or narrow and having shields with strong levogyral curvature; they are tightly interlocked to form a robust spherical to subspherical coccosphere. (Murray et Gaarder, 1980 (in Heimdal andGaarder, 1980), have been repeatedly found and it is clear that the former C. rigidus is the holococcolithophore phase of C. leptoporus (Kleijne, 1991(Kleijne, , 1993Cortés, 2000;Renaud and Klaas 2001). Moreover, Geisen et al. (2000) presented a well formed combination coccosphere with holococccoliths of Syracolithus quadriperforatus (Kamptner) Gaarder surrounding a complete coccosphere of C. leptoporus and suggested a cryptic speciation of the heterococcolithophore morphology, as a possible explanation for these very different associated holococcoliths. Nevertheless three different morphotypes of C. leptoporus (Kleijne, 1993;Knappertsbusch et al. 1997) have been recognized and these different holococcoliths could correspond to different C. leptoporus morphotypes. Until more details are known, we report here C. rigidus as the well recognized holococcolith-bearing phase of C. leptoporus and we leave S. quadriperforatus inside the Calyptrosphaeraceae group.

Oolithotus antillarum
The specimens found in the course of the present study have a smooth surface and a very small depression on the distal face instead of a real pore as seen in the specimens figured by Okada and McIntyre (1977), Hallegraeff (1984), and Kleijne (1993).

Coccoliths of UNCERTAIN AFFINITIES
Family PAPPOSPHAERACEAE Jordan et Young, 1990 Family of minute, lightly-calcified coccolithophores, mainly known from high-latitudes, with holo-and heterococcolith phases (Thomsen et al, 1991;Thomsen and Buck, 1998). The characteristic heterococcolith of this family is the pappolith (Tangen, 1972;Norris, 1983), a coccolith with a narrow murolith rim of non-overlapping elements, which may have a central spine supporting a calyx of four plates (Young and Bown, 1997). In the genus Papposphaera, all of the pappoliths on the coccosphere have a spine, whereas in the genus Pappomonas, the coccosphere also possesses pappoliths without a central spine (Manton et al., 1976a). Nevertheless, it has been pointed out that these two genera are similar and eventually might be merged if and when more species are discovered (Thomsen et al., 1988). The known Papposphaeraceae species have been described and studied essentially from high-latitude sea waters, and this is possibly the reason for the large number of undescribed species observed in this NW Mediterranean study, and for the absence of most of the known species. Of the formally described species, only Papposphaera lepida Tangen, 1972, was recognized in NW Mediterranean waters.
Genus Papposphaera Tangen, 1972 The heterococcospheres have pappoliths with processes and with pentagonal plates that form the rim. The shape of the process and the morphology of the base plate are used to separate the different species. Thomsen et al. (1991) showed that species of Papposphaera and species placed in the genus Turrisphaera are life history stages of a single organism. Tangen, 1972 ( Fig. 65) Papposphaera lepida Tangen, 1972, pp. 172, 175, 176, 177 The basal part of the pappoliths is from elliptical to subcircular, the rim composed of a crown of nonoverlapping, distally pointed, pentagonal elements and a proximal ring of narrow rod-shaped elements; the central spine is usually long and delicate with four ridges which diverge at the bottom plate forming a distinct axial cross-bar; at the top of the appendage there is a wide structure, the calyx, formed of four flattened lobes, most having shallow incisions giving a flower-like appearance. This calyx structure can be highly variable in shape and can even appear completely square, as described and figured by Thomsen and Buck (1998) from Mexico (Bahia de los Angeles, Sea of Cortez). In addition to the rim and the central area, the length and width of the spine can also be very variable.
The coccosphere has clearly varimorphic pappoliths with larger shafts at one pole and very short shafts in other parts of the coccosphere. The pappoliths have an elliptical base plate with a crownshaped rim and axial crossbars which appear to act as struts to support the central stem; there are no visible collar around the distal part of the stem, below the central calyx, and the calyx structure is formed of "four quasi-rectangular, diverging plates". The number of specimens studied from NW Mediterranean waters was 8. Coccospheres possess around 60-110 coccoliths. Dimensions. Coccosphere diameter 4.1-5.6 µm; coccolith base length 0.5-0.8 µm; coccolith height (0.4-) 0.7-1.0 (-1.6) µm.

Papposphaera sp. type 2 (Figs. 66C, D)
Coccosphere with dimorphic coccoliths, having at one pole pappoliths with larger shafts and a distal structure composed of four small rod-shaped elements perpendicular to the shaft; the other pappoliths have shorter shafts that end in four small diverging rods.
The studied specimen consists of 8 coccoliths with long spines and about 34 coccoliths with small central process.

Papposphaera sp. type 3 (Figs. 67A, B)
Coccosphere with varimorphic coccoliths having at one pole pappoliths with larger stems and a distal structure composed of four diverging sepal-like elements; the other pappoliths mostly have smaller sepal-like elements, but some are tipped by four petaloid elements resembling the distal structure a flower (further specimens are required to clearly establish the extent of variability of the coccoliths).
Papposphaera sp. 3 resembles the described Papposphaera bourrelly Thomsen et Buck, 1998, differing mainly in having varimorphic coccoliths and in having different sepal-like structures, with no collar at the base.

Papposphaera sp. type 4 (Figs. 67C, D)
Coccosphere with varimorphic coccoliths. The proximal side of the coccoliths is typical of Pap-posphaera, but the distal side is not a typical calyx; in the studied specimen the distal part of the stem splits into four triangular lamina, joined on their long side and with the distal part serrated.
The studied specimen consists of ca. 50 coccoliths.
?Papposphaera sp. type 5 (only three elements compose the distal structure) (Figs. 68A, B) Coccosphere with varimorphic coccoliths, which have stems of different sizes and diverse distal structures; the proximal side of the coccoliths is typical of Papposphaera (elliptical base plates with crownshaped rims and an axial crossbar), but the distal side does not have the typical calyx-like structure with four elements, but rather a distal structure resembling a propeller composed of three triangular elements.
The two studied coccospheres have ca. 90 to 120 coccoliths.
?Papposphaera sp. type 6 (only three elements compose the distal structure) (Figs. 68C, D) Coccosphere with varimorphic coccoliths. The distal structure is characteristically composed of three elements in the form of large triangular blades which start near the base plate, leaving no space for a real stem.
Papposphaera holococcolithophore ("Turrisphaera") phase sp. type B (Figs. 69C, D) The proximal part of the holococcoliths is typically "apple-core" shaped, but they become flattened distally, ending in a very characteristic distal structure which resembles a leaf.
Genus Pappomonas Manton et Oates, 1975 The heterococcospheres have pappoliths with and without central spine; the rim of all coccoliths is constructed of pentagonal plates. Thomsen et al. (1991) reported that species of Pappomonas and species of the holococcolithophore Trigonaspis Thomsen (Thomsen, 1980) sometimes form combination cells, and concluded that the taxa involved (P. flabellifera var. borealis and Trigonaspis cf. diskoensis Thomsen, 1980) are different phases of the same life-cycle. However, preliminary results indicated that P. virgulosa forms combination cells with Balaniger balticus Thomsen and Oates (results referred from Ostergaard in Thomsen and Oates, 1978).
Pappomonas sp. type 1 (Fig. 70A) Body coccoliths with central area structure of two concentric rings and a conspicuous bar across the minor axis. The pappoliths with spine have a long central stem tipped by four small rods.
Pappomonas sp. type 1 resembles P. virgulosa in having the apical pappoliths tipped by four rods, but differs from it in having longer stems, with much shorter ends and in having body coccoliths with higher and more developed rims.
Pappomonas sp. type 2 (Fig. 70B) Body coccoliths elliptical with plate elements covering the entire base plate. Apical pappoliths having a rounded base plate with a cross-bar, a long central stem and a large obpyramidal distal calyx. The rim is characteristically low in all the coccoliths, showing no clear pentagonal plates.
The calyx of coccoliths of Pappomonas sp. type 2 resembles that of Papposphaera obpyramidalis, but the stems of the latter species are shorter, the base plates are different, and moreover Pappomonas sp. type 2 possesses elliptical coccoliths without a central process.

Pappomonas sp. type 3 (Figs. 70C, D)
Body coccoliths with a cross-bar in the base plate and a small nodular central structure. The pappoliths with calicate spine have a long central stem and a distal structure composed of four varimorphic sepallike elements.
?Pappomonas sp. type 4 (Fig. 71A) The coccosphere consists of three different types of coccoliths. The body coccoliths consist of elements that form two concentric rows and a bar across the minor axis. Apical pappoliths have a long circular central spine with no calyx. There is another coccolith type which has a shorter circular spine.
Note that it would be necessary to redefine the genus Pappomonas if this species was to be included; by definition, members of this genus have two types of coccoliths, both with a calicate spine, but this species has three types of coccoliths and those with a spine have no calyx. Nevertheless, the structure of the central area and the rim of both types of coccoliths (with and without spine) are clearly typical of this genus.
?Pappomonas sp. type 5 (Fig. 71B) Body coccoliths have elements that form two concentric rows and a bar across the minor axis. Apical pappoliths have a long, bent, circular central rod. A few antapical coccoliths have a shorter circular rod.
This specimen resembles ?Pappomonas sp. type 4, but has smaller coccoliths with longer and bent spines.
The studied coccosphere consists of ca. 105 coccoliths; 4 with short spine, about 21 with long bent spine, and 80 without spine.
Genus Picarola Cros et Estrada (in press) This genus, which resembles to Papposphaera, has some characteristics that suggest affinities with Vexillarius cancellifer Jordan et Chamberlain, 1993b. Coccoliths have a curved four-sided process and a rim consisting of quadrilateral elements. Qualitative X-ray analysis of several specimens of this genus have proved the calcium content of the coccoliths.
Coccosphere can possess three different types of coccoliths. Body coccoliths have a highly curved appendix, which finishes in a pointed end. Circumflagellar coccoliths have a straight and high wall and a large and slightly curved appendix, which finishes abruptly in a truncated end. Antapical coccoliths (only 0 to 2) have a flaring wall and a nearly straight appendix, which finishes in a pointed end.
Picarola sp. (Figs. 72C, D) Coccosphere with different types of coccoliths. Coccoliths with a curved central process that gradually flares distally, resulting in a characteristically hollow distal structure with pointed endings. The central area of the base appears to have a diagonal rather than an axial cross-bar, and the rim consists of different sized rectangular plates which give a characteristic side profile to the coccolith base.

Genus Type A
Monomorphic coccoliths with a long central structure and a rim formed of rectangular plates.
Genus Type A, species type 1 (Fig. 71C) Coccoliths having long and sharp spines without distal structure.
Genus Type A, species type 2 (Fig. 71D) Coccoliths with a long, square central process that flares and bends distally, resulting in a very characteristic feather-like structure.
Family CERATOLITHACEAE Norris, 1965 Cells with two extremely different types of structure: a single horseshoe-shaped nannolith and ring-shaped coccoliths which adhere together to form a sphere that encloses the protoplast and the single horseshoe-shaped coccolith. It was recently discovered that the species has an alternate phase with another coccolith type: a subcircular planolith with an open central area.
Genus Ceratolithus Kamptner, 1950 The ceratoliths are the horseshoe-shaped nannoliths characteristic of this genus; they are robust and somewhat asymmetrical in form, with one arm being slightly shorter than the other. The coccosphere also bears ring-shaped coccoliths, named hoop-like coccoliths, which are numerous but delicate. Several cells, each with a ceratolith, may be present within a single sphere constructed by hoop-like coccoliths. It is now known that the species can generate another kind of coccolith, formerly known as Neosphaera cocccolithomorpha (Alcober and Jordan, 1997;Young et al., 1998, Cros et al., 2000bSprengel and Young, 2000). Kamptner, 1950 Fig. 73. The cells of Ceratolithus cristatus have three very different types of coccoliths: a) ceratoliths, which may be considered horseshoe-shaped nannoliths because they do not have the symmetrical characteristics of heterococcoliths and holococcoliths; b) hoop-like coccoliths which are a ring formed of connected crystal-units; c) the coccoliths belonging to the former Neosphaera coccolithomorpha Lecal, circular heterococcoliths with a single shield and a tube. Each one of these coccoliths can appear in at least two varieties: a) Ceratoliths. Three types have been described: Ceratolithus cristatus var. cristatus which is the typical form; Ceratolithus cristatus var. telesmus (Norris) Jordan et Young, a form with longer arms that curve together to almost touch (morphotype first described as Ceratolithus telesmus Norris, 1965); Ceratolithus cristatus forma rostratus which is an ornate form with an apical beak or rostrum (this form was summarily described by Borsetti and Cati (1976), but they did not propose a formal description, so the epithet "rostratus" it is not yet validated). b) Hoop-coccoliths. With at least two forms: robust hoops with a thick ring and more delicate hoops with thinner rings, but of larger size (Young et al. 1998). c) "Neosphaera" coccoliths. They vary considerably in size and diameter of the central-opening; two main varieties are distinguished: var. coccolithomorpha and var. nishidae (Kleijne, 1993).

Ceratolithus cristatus
In NW Mediterranean waters, the Ceratolithus cristatus coccolith types are: Ceratolithus cristatus forma rostratus, delicate hoop-like and "Neosphaera" type var. nishidae. This appears to be a very characteristic association , leading to the suspicion that the three coccolith types belong to the same coccolithophore taxon.
Coccospheres can have 1-2 ceratoliths, a very variable number of hoop-like coccoliths and around 21 coccoliths of the type "Neosphaera".

Polycrater-Alisphaera-Canistrolithus,
provisional group of genera Two combination coccospheres were observed from NW Mediterranean waters with coccoliths of Polycrater and of the genus Alisphaera (Cros, 2001; Plate 87, figs. 1-6). Two other combination coccospheres were observed involving Polycrater coccoliths and Canistrolithus coccoliths (Plate 88, figs. 1-6). The Polycrater specimens associated with Alisphaera and Canistrolithus were of different morphological types. The two genera, Alisphaera and Canistrolithus, are recognized as very close in the literature (Jordan and Chamberlain, 1993a) and it is noteworthy that these three genera, Polycrater, Alisphaera and Canistrolithus, present common characteristics in both, coccolith morphology and coccosphere arrangement. All three genera show a longitudinal asymmetry of their coccoliths and a general coccolith arrangement based on approximately regular meridian rows around the cell. The presence of horns, spines and extended protrusions is common in the coccoliths of Polycrater, Alisphaera and Canistrolithus. Inside the framework of these findings it is hypothesised that these three genera may represent an unusual sub-group of coccolithophores in which, possibly, the aragonitic Polycrater coccoliths substitute for holococcoliths in their life-cycle (Cros et al., 2000a). At the moment, in the present Atlas, we leave the three taxa with their respective usual names, but we remove Alisphaera and Canistrolithus from the Syracosphaeraceae family to group them with the genus Polycrater, which was considered incertae sedis.
Genus Alisphaera Heimdal, 1973, emend. Kleijne et al., 2001 Alisphaera genus presents elliptical coccoliths with a short tube, a proximal flange and a distal flange. Alisphaera coccoliths are clearly asymmetrical with respect to the major axis, having one half of the distal flange wider than the other; usually the more developed part shows some characteristic spike or protrusion specific of the species. The central area usually presents a longitudinal, slightly Sshaped fissure and nodules along the inner periphery of the distal flange, specially on the narrow side.
Until now, the genus Alisphaera has been included in the family Syracosphaeraceae, but the fact that its coccoliths are not real caneoliths is recognized in the literature, some authors referring to them as placolith-like coccoliths (Young and Bown, 1997b) or as modified caneoliths (Chrétiennot-Dinet, 1990;Jordan and Chamberlain, 1993a). A new and extensive review of this genus is giving in Kleijne et al. 2001. Following the discovery of coccospheres combining Alisphaera with the nannolith-bearing genus Polycrater, it seems advisable to group these genera with the other associated taxa. Heimdal, in Heimdal et Gaarder, 1981 (Figs. 74A, B) Alisphaera capulata Heimdal, in Heimdal and Gaarder, 1981, p. 39-40, pl. 1 Fig. 3-4 ; Kleijne, 1993, p. 233, pl. 2, fig. 7; Kleijne et al., 2001, p. 587, Figs. 22-24. The coccoliths possess an extension like a flat handle on the external part of the wider flange; this raised part is more or less inclined to the left; the central area appears to have a solid base plate without a fissure.
Dimensions. Coccosphere long axis ca. 8 µm; coccolith length 1.6-1.9 µm. Kleijne et al. 2001 Cocccoliths show a variable morphology of the distal flange extension and they are considered dimorphic and even varimorphic (Kleijne et. al. 2001). Most of the coccoliths have on the wider distal flange a pointed projection like a beak or asymmetrical spine, a longitudinal irregularly shaped opening in the central area and nodules. Cocccoliths without the pointed protrusion occur on the coccosphere. A well formed combination coccosphere of this species with a Polycrater with holes, reminiscent of Gaudí's architecture is figured in Figs. 77A, B.

Alisphaera pinnigera
The coccoliths have a longitudinal fissure in the central area and small tooth-like protrusions along their inner margin; some coccoliths have a vertical protrusion like a flat triangle with its base positioned perpendicularly on the wider flange in the direction of the short axis of the coccolith.
Most coccospheres are presumably broken, so coccolith numbers (128,164,174,244 and 342) may be underestimated.

Alisphaera quadrilatera
The cocoliths possess a flat and obliquely raised protrusion, which is more or less five-sided counting the wide base, with four external sides, situated in the centre of the wide distal flange, covering a slit present in the outer part of the same flange. Central area shows longitudinal fissure.
This taxa differs from Alisphaera ordinata mainly in possessing a polygonal protrusion instead of a very broad protrusion extended over nearly all the distal flange.

Alisphaera unicornis
Coccoliths have a pointed protrusion like a horn, eccentrically placed, on the wider distal flange, although a few coccoliths on the coccosphere may lack this obliquely raised tooth. Central area with a longitudinal irregularly shaped fissure. Nodules usually absent.
It is difficult to distinguish between Alisphaera unicornis and A. spatula Steinmetz, 1991, but the smaller sized coccoliths of A. spatula possess nodules and a flat blade-shaped element with a pointed extension on top, which is centrally placed instead of a horn, which usually is asymmetrically placed in A. unicornis.
Genus Canistrolithus Jordan et Chamberlain, 1993 Coccoliths are narrowly elliptical to oblong. They have a high and composite wall and are asym-metrical along the major axis, having one half of the distal flange wider than the other; usually the more developed part shows a single upright thorn and the narrower half can presents nodules along the inner periphery of the flange; an organic membrane appears to cover the proximal central area of the coccolith.
This genus has been classified inside the family Syracosphaeraceae because the authors who described it recognized the resemblance with the genus Alisphaera (Jordan and Chamberlain, 1993a). In the present study only two specimens were observed, both being combination coccospheres with coccoliths of Polycrater. Taking into account these combinations with the nannolith bearing genus Polycrater (Figs. 78A, C, D and 79A, B), it seems necessary to group Canistrolithus with Polycrater and Alisphaera, and to define this newly emerging genus perhaps within a new higher taxon.
Canistrolithus sp. 1 (Fig. 78B) Coccoliths with and without spines; the spine is placed on the more developed part of the flange, near the outer edge; the central area is unfilled or possesses a proximal organic membrane.
This species can be associated with Polycrater on combination coccospheres.
Canistrolithus sp. 1 differs from C. valliformis and the species figured by Reid (1980), p. 158, 160, pl. 4, fig. 8-11, in having coccoliths with a lower wall, wider flange (particularly in its narrow part) with neither nodes nor peg-like structures and with spines placed in a less central position.
The more complete coccosphere consists of around 212 coccoliths.
Genus Polycrater Manton et Oates, 1980 Coccosphere with a close packed layer of delicate bowl-shaped coccoliths arranged with the concavities directed outwards; this kind of coccolith has also been defined as aragonitic square-sectioned cones. This genus contains a single recognized species, but many different forms were found in the course of the present work. Hence the genus description must be emended in order to embrace all of the possible new species. Moreover, in the studied samples it has been found that different Polycrater taxa can form combination cocospheres with different Alisphaera and Canistrolithus species.
The coccosphere has numerous very small coccoliths of angular architecture wedged together with the short coccolith axis presumably in a polar direction. The coccoliths are asymmetrical in relation to the major axis, with one half broader than the other; they may or may not have a bowl-like distal side, but all of them present a cross-like proximal side.
The special coccoliths have two well differentiated parts comparable to a flower, as clearly represented in fig. 5 of Manton and Oates (1980): a proximal part with sepal-like components and a distal part with petal-like components. Usually the specimens have four petal-like components that build a bowl or cone of squared section; on the external part of the angular joins there are buttresslike extensions that connect with the sepal-like proximal structures. Manton et Oates, 1980 (Figs. 80A, B) Polycrater galapagensis Manton et Oates, 1980, p. 102, 103, figs. 1, 3, 4, 5, 6.; Thomsen et al. 1994, figs. 10.6, 10.7. Polycrater sp. Chrétiennot-Dinet, 1990 This species has bowl-shaped coccoliths with distal concavities and a cruciform external thickening that define the four petal-like lobes and four sepal-like structures with undulate edges overlaying the cruciform thickenings on the proximal side. Coccoliths composed of aragonite (Manton et Oates, 1980).

Polycrater galapagensis var. A (with nodes)
(Figs. 79C, D) Winter and Siesser, 1994, p. 141, fig. 128. This coccosphere closely resembles P. galapagensis, but the distal part of the smaller half of coccoliths has small nodes and usually a v-shaped inci-sion in the higher corner. This Polycrater taxa can form associations with Canistrolithus sp. 1 (Figs. 78A,C,D and 79A,B).
Polycrater sp. (with holes, reminiscent of Gaudí's architecture) (Figs. 77C, D) Polycrater galapagensis auct. non Manton et Oates, Giraudeau and Bailey, 1995, pl. 5, fig. 11. This coccosphere resembles P. galapagensis, but coccoliths have two lenticular holes in the larger half, near the centre, one on each large petal-like element; upper corner shows a slender leaf-like extension. This Polycrater taxa can form associations (Figs. 77A,B) with Alisphaera gaudii and should be considered as a "Polycrater" form of the Alisphaera gaudii.
This Polycrater has a characteristic appearance reminiscent of the shapes created by Gaudí.

Polycrater sp. (with slit) (Figs. 80C, D)
This coccosphere resembles P. galapagensis, but coccoliths have a distal slit near the lower corner, in sinistral position, and usually have a v-shaped incision in the higher corner.

Polycrater sp. (with lip-like borders) (Figs. 81A, B)
Genus and species indeterminable, Nishida, 1979, pl. 21 fig. 6. This coccosphere resemble P. galapagensis, but coccoliths are smaller (0.3 to 0.5 µm along the major axis) and have the borders of the larger half bent like lips; the sepal-like parts (proximal side) are small with a very simple structure.
Dimensions. Coccosphere diameter (6-) 8.5-9.5 (-11.5)  The coccosphere has very small coccoliths, with the sepal-like structures formed of a very little cross. The size of each coccolith is around 0.2 µm.
Polycrater sp. (two petal-like structures very modified; ladle-like coccoliths) (Figs. 82A, B) The coccosphere has an unusual spiny shape. The coccoliths have the sepal-like structure similar to the other Polycrater species, whilst the petal-like structure is highly modified: two petal-like elements are very reduced with the corner highly extended forming a tall rod; the other two petal-like elements are normally constructed, the entire structure thus resembling a ladle.
The coccosphere has a spiny shape. The coccoliths have the sepal-like structure similar to the other Polycrater species, whilst the petal-like structure is completely modified: two petal-like elements are very reduced with the corner highly extended forming a stick of variable width; there are no more petallike elements.
The species Erciolus spiculiger Thomsen (Thomsen et al. 1995) appears morphologically related with this Polycrater sp., but the coccoliths of Erciolus spiculiger do not show the cross sepal-like proximal structures that possess Polycrater sp. coccoliths.

Umbellosphaera tenuis
The coccosphere consists of coccoliths of diverse size which can be separated in two main types: (a) small umbelloliths or micrococcoliths with an elliptical central area; (b) umbelloliths or macrococcoliths which are larger with a subcircular central area. Both types have a very short tube, a practically nonexistent proximal shield, and a greatly extended distal shield with highly variable ornamentation. Micrococcoliths are usually present in a proximal layer on large coccospheres; macrococcoliths are always present and the different ornamentation of their distal shield could be of considerable ecological interest (Kleijne, 1993).
Genus Florisphaera Okada and Honjo, 1973 Coccospheres in the form of a multi-petaled flower. Coccoliths in the shape of polygonal plates, classified as nannoliths; to form the coccosphere, these nannoliths are arranged all in the same direction and show a concentric pattern in top view, forming a rosette when spread open in apical view. Okada and Honjo, 1973 (Figs. 84C, D and 85A-C) Florisphaera profunda Okada and Honjo, 1973, pp. 373-374, pl. 1, fig. 6, pl. 2, figs. 4-6;Nishida, 1979, pl. 16, fig. 3-4;Young, 1998, p. 254, pl. 8.6, fig. 20, 25. Coccoliths are small irregular plates formed of single calcite units. A peg-like structure on the base of some specimens may indicate a second crystal unit. Okada and Honjo (1973) separated the species in two varieties (A and B) on the basis of the differences in coccolith shape and size. Later, the varieties were validated as var. profunda and var. elongata (Okada and McIntyre, 1977;, var. profunda being smaller, more quadrangular and having a zigzag pattern of lines at the base and top (Fig. 85B), while var. elongata is larger in size, with side profiles tapered towards the bottom, and the top profile straight with an outstanding peak (Fig. 85A).

Florisphaera profunda
Among NW Mediterranean specimens, some possess clearly identifiable coccoliths of both reported varieties. Other specimens possess coccoliths very different from both recognized varieties, e.g. the specimen figured in Fig. 85D, the coccoliths of which are notably different in shape and have a conspicuous distal spine. More observations are required in order to be able either to distinguish varieties or to acknowledge that they are not consistently separable, as suggested by Young (1998).
Family CALYPTROSPHAERACEAE Boudreaux et Hay, 1969 This family embraces all the holococcolithophores, which have only holococcoliths in their known life cycle. Holococcoliths are composed of microcrystals arranged in an ordered manner. Parke and Adams (1960) reported that a culture of a heterococcolithophore, Coccolithus pelagicus, had given rise to cells of a holococcolithophore, the former Crystallolithus hyalinus. As a result of several other observations of hetero-holococcolith associations, the family Calyptrosphaeraceae at present only includes the holococcolithophore species for which no heterococcolith stage is known. The number of such species is rapidly diminishing as research advances. Several species and even genera (Crystallolithus Markali, emend. Gaarder 1980 (in Heimdal andGaarder, 1980); Turrisphaera Manton, Sutherland and Oates, 1976b) have been taken out of this family in recent literature (Kleijne, 1991;Jordan and Kleijne, 1994;Jordan and Green, 1994;Young and Bown, 1997b) and are included among their heterococcolithophore counterparts.
The following descriptions of genus, species and coccolith morphology are mainly based on the revision work of Kleijne (1991); but here the species are alphabetically ordered following Jordan and Green (1994) and not separated by their monomorphism or dimorphism, since in some genera it is difficult to identify if they have mono-or dimorphic coccospheres.

Anthosphaera fragaria
A single "hybrid" collapsed coccosphere showing dimorphic endothecal coccoliths of Syracosphaera molischii with both body and circumflagellar coccoliths of Anthosphaera fragaria (Fig.  112A) was found in the studied samples. This collapsed coccosphere was not considered a conclusive combination due to the observed bad condition of the specimen.
Anthosphaera cf. fragaria Kamptner, 1937 emend. Kleijne, 1991 (Fig. 86C) Two specimens studied are similar to A. fragaria, but differ in that both calyptrolith-like coccoliths and fragarioliths are smaller in size and have larger pores.

Anthosphaera periperforata
Body coccoliths with a narrow rim connected to the distal dome by ca. 16 radial rows of crystals separated by perforations. Circum-flagellar fragarioliths are constructed by a rim of crystals connected to a pointed leaf-like process by long rows of one crystal width. Three different types: 1, 2 and 3 can be recognized within this species.
-A. periperforata type 1 (Figs. 87A, B). Kleijne, 1991, figured this type 1 in pl. 9, figs. 5-6 The body coccoliths of this type have the shortest connecting rows between the rim and the distal dome; this dome is highly vaulted and in some antapical coccoliths bears a small spine. Circum-flagellar coccoliths with pointed distal process and no central rows.
The body coccoliths have rows of 4 to 5 crystals that connect the rim with the distal dome which is highly vaulted; in some antapical coccoliths the dome bears a small spine. Circum-flagellar coccoliths have a pointed distal process and usually central rows of one crystal width.
-A. periperforata type 3 (Figs. 87D). This type differs from types 1 and 2 in having nearly flat body coccoliths, with long rows of about 6 crystals connecting the rim with the reduced distal dome.
Anthosphaera sp. type A (origami art) (Fig. 88A) The body coccoliths have a very characteristic structure in the shape of a small origami paper boat, instead of the simple dome. Circum-flagellar fragarioliths heavily ornamented.
Anthosphaera sp. type B (Fig. 88B) The body coccoliths have a thin rim constituted of a ring, one crystal wide, and a simple dome formed by only some crystals. Circum-flagellar fragarioliths have a flat leaf-like process with nearly straight sides.
The studied specimen consists of ca. 8 fragarioliths and ca. 80 body coccoliths.
Dimensions. Coccosphere long axis ca. 4.5 µm; body coccolith length ca. 0.6 µm; circum-flagellar coccolith height ca. 1.3 µm; Anthosphaera sp. type C (Fig. 88C, D) The small body coccoliths of this species appear to be very simple calyptroliths which, in some cases, have lost the central part leaving only the rim; circum-flagellar coccoliths can appear as very simple and slender fragarioliths. This holococcolithophore might thus be considered to be a very simple representative of the genus Anthosphaera.

Calicasphaera concava
The calicaliths have a proximal ring of crystallites and a concave wall, which widens broadly towards the distal end.
Body calyptroliths with a short and distally widening tube that surrounds and protrudes over the distal surface, which has the form of a highly vaulted roof. Circum-flagellar zygoliths with a broad process ending in a sharply pointed protrusion.

Calyptrolithina wettsteinii
C. wettsteinii is now considered to be the holococcolith phase of Coronosphaera mediterranea (see p. and Figs. 28C, D).
Genus Calyptrolithophora Heimdal in Heimdal et Gaarder, 1980 Coccosphere with dimorphic coccoliths. Both body and circumflagellar coccoliths are calyptroliths with straight sides and a straight rim, which has a distal prominence. The body calyptroliths have a nearly flat distal side, while circum-flagellar calyptroliths show a highly convex distal part.

Calyptrolithophora gracillima
The body calyptroliths have a rounded distal protrusion. The protrusion of circum-flagellar calyptroliths is larger, sometimes forming a bridge crossing the short axis of the coccolith.
Genus Calyptrosphaera Lohmann, 1902. This genus bears dome-shaped calyptroliths, and is usually considered to have monomorphic coccoliths; nevertheless, some coccoliths near the flagellar area may be higher than the others and may even possess a papilla or a short distal spine. Borsetti et Cati, 1976 Figs. 92C, D.
Calyptroliths consisting of a broad rim and a dome-shaped central area with one central pore and 7 large pores surrounding the base of the dome area; these latter pores are characteristically straight on the proximal side of the coccolith and arched distally. Some calyptroliths, presumably from the circumflagellar area, are higher and can bear a conspicuous spine.

Calyptrosphaera sp. (smaller heimdaliae) (Figs. 93C, D)
The specimens closely resemble C. heimdaliae, but have smaller coccoliths with lower tubes and a larger number of pores (around 20) which are smaller and square-shaped. An added character is that the microcrystallites are packed more closely.
It is remarkable that some specimens appear to be more similar to C. heimdaliae than others; this might be a taxon possibly related with C. heimdaliae, or be morphological variants of this latter species.
This genus is recorded in the recent check-lists of the extant coccolithophores and Haptophyta (Jordan and Kleijne, 1994;Jordan and Green, 1994) with only three species (C. gracilis, C. strigilis and C. tyrrheniensis), while in the extensive holococcolithophore revision of Kleijne (1991), this genus includes two more species described in open nomenclature (C. sp. type A and C. sp. type B). In the present NW Mediterranean study, the Corisphaera specimens display a high diversity of morphologies, but only three of the five above enumerated species can clearly and repeatedly be recognized. A deeper study of Corisphaera should be carried out, including a review of the old literature of LM studies and further detailed observation of LM and parallel SEM samples, to properly clarify this genus. Plate 62 includes only the clearly classified Corisphaera species and Plate 63 represents the high diversity of Corisphaera morphologies.

Corisphaera tyrrheniensis
The body zygoliths as well as the larger circumflagellar zygoliths are constructed of loosely connected rows of microcrystallites, resulting in a characteristic perforated appearance.
Corisphaera sp. (aff. type A of Kleijne, 1991) (Figs. 96C, D) Body zygoliths closely resembling those of Corisphaera sp. type A (Kleijne, 1991), but without the well-formed low, one crystal thick, marginal rim. Circum-flagellar coccoliths without the double-layered wall showed in Corisphaera sp. type A. The specimens appear to have larger crystallites than those of Corisphaera sp. type A. Some specimens appear more fragile, possibly representing a variety of the species.
Corisphaera sp. (body zygoliths with pointed bridge) (Fig. 97B) Body zygoliths have a high wall and a wide, high and thin bridge which is pointed distally; this bridge forms a real mid-wall inside the zygolith.

Daktylethra pirus
Although this species is considered to have monomorphic coccoliths, presumed circum-flagellar coccoliths with a short conical extension protruding from the central area are observed (Throndsen, 1972;Heimdal, 1993; Fig. 98A). Geisen et al. (2000) presented combination coccospheres with heterococcoliths of S. pulchra and holococccoliths of Daktylethra pirus (Kamptner) Norris, and suggested a cryptic speciation, not clearly recognizable from the heterococcolithophore morphology, as a possible explanation for these very different holococcoliths associated to Syracosphaera pulchra. More work in this matter is necessary to ascertain whether Daktylethra pirus is part of the life-cycle of S. pulchra; in the meantime it seems better to consider Daktylethra pirus as independent of S. pulchra.
A group of coccoliths which appeared to be a mixed collapsed coccosphere of Syracosphaera nodosa and Helladosphaera cornifera is illustrated in Fig. 113D. However, this collapsed coccosphere was not considered as a conclusive combination coccosphere (Cros et al., 2000b).
Genus Homozygosphaera Deflandre, 1952 This genus bears zygoliths, and is considered to contain species with monomorphic coccoliths; nevertheless, some coccoliths near the flagellar area may be higher than the others and may even possess a papilla.
The zygoliths have a proximal tube that seems double-layered and also a distal, robust bridge, which sometimes is very broad. The circum-flagellar coccoliths have a higher bridge topped by a small protrusion.

Homozygosphaera triarcha
Several coccoliths, presumably from the circum-flagellar area, have a more elevated protrusion with a higher conical process that has a spine-like appearance at the tip.
Genus Periphyllophora Kamptner, 1937 Periphyllophora was considered as a monospecific genus having coccospheres consisting of monomorphic helladoliths. Recently, Cros et al. (2000b) demonstrated the association of the only species in this genus with the heterococcolithophore Syracosphaera anthos. (Schiller) Kamptner, 1937 P. mirabilis is now considered as the holococcolith phase of Syracosphaera anthos (p. and Fig. 35B.

Periphyllophora mirabilis
Genus Poricalyptra Kleijne, 1991 Coccosphere with dimorphic coccoliths. Body coccoliths are calyptroliths with a perforated tube wall and a flat distal surface with slits or pores and a prominent rim. Circum-flagellar coccoliths are helladoliths.
The body calyptroliths have large pores (usually 6) in the distal side, and, following the minor axis, one very short row of extra crystallites. Circum-flagellar helladoliths with no extra pores.
Genus Poritectolithus Kleijne, 1991 Coccosphere with dimorphic coccoliths. Body holococcoliths with characteristic strings of crystallites on the distal face. Circum-flagellar coccoliths are helladoliths. Within Poritectolithus there are two clearly distinguishable groups; one with body coccoliths like calyptroliths and the other with body coccoliths like zygoliths. N.B. Kleijne (1991) described this genus as possessing zygolith-like body coccoliths.

Poritectolithus taxa bearing calyptrolith-like body coccoliths
This group contains the Poritectolithus species with calyptrolith-like body coccoliths which have a closed roof. These calyptroliths can be flat like laminoliths, e.g. Poritectolithus sp. 1, or with the central area of the distal side slightly convex, e.g. Poritectolithus tyronus, or like real calyptroliths with a distally widening wall, e. g. Poritectolithus poritectus.
The coccosphere consists of flat body calyptroliths having a rim two crystallites high. Circum-flagellar helladoliths with a basal part similarly constructed and a straight and flat leaf-like protrusion.

Poritectolithus poritectum
The body holococcoliths are more calyptrolithlike than zygolith-like; they are constructed of relatively large crystallites which form a wall and a distal side with characteristic rows and a conspicuous rim; several neighbouring rows appear to present some kind of symmetry which is also clearly shown in the micrographs of Heimdal and Gaarder (1980); the wall slightly widens distally and protrudes the neighbouring distal roof. Circum-flagellar helladoliths with a flared wall and a large protrusion.

Poritectolithus taxa bearing zygolith-like body coccoliths
This group includes the Poritectolithus with zygolith-like body coccoliths which have a bridge consisting of several irregularly placed rows of crystals. These zygolith-like holococcoliths can have a slightly vaulted bridge, e.g. Poritectolithus sp. 2, or possess a very high and vaulted bridge, e.g. Poritectolithus maximus Kleijne, 1991. Poritectolithus sp 2.
(Figs. 102C, D) Body holococcoliths are zygolith-like coccoliths with convex rows of crystallites, irregularly placed, forming a bridge. Circum-flagellar helladoliths have a triangular-shaped leaf-like protrusion, which is wider than high. The coccoliths are constructed of microcrystals separated by perforations.
The studied specimen closely resembles the specimen figured in Kleijne (1991) as Poritectolithus poritectum and that figured, with the same name, in Winter and Siesser (1994), fig. 185.

Sphaerocalyptra quadridentata
This species was found as part of a combined, but collapsed, specimen with Rhabdosphaera clavigera (Fig. 114A) and coccoliths of the same species were found (Fig. 114B) in an apparently random grouping (see discussion in R. clavigera text).
Sphaerocalyptra cf. adenensis Kleijne, 1991 (Figs 103C, D) Body calyptroliths taper abruptly from the base. Circum-flagellar calyptroliths are notably higher than body calyptroliths, tapering slightly towards near the base and more abruptly distally, forming a pointed protrusion that sometimes appears bent. The microcrystallites are closely packed and appear arranged in concentric rows.

Sphaerocalyptra sp. 3 (string-formed calyptroliths) (Figs. 105B-D)
Body calyptroliths consist of a thin basal ring of crystals connected to about six strings of one crystallite width which form the perforate calyptrolith; where these strings meet, a thin central distal pro-trusion is formed. Circum-flagellar calyptroliths are notably higher (i.e. with longer strings).
Sphaerocalyptra sp. 6 (rings-shaped residual calyptroliths) (Figs. 106C, D) The small body calyptroliths are formed of a basal ring with some crystallites that appear to be the residual part of the calyptrolith. Circum-flagellar calyptroliths have a rim two crystals high and a long and straight spine.
Monomorphic coccosphere consisting of laminoliths. Certain representatives of this genus form associations with Helicosphaera  Syracolithus catilliferus (Kamptner, 1937) Deflandre, 1952 S. catilliferus is now considered as the holococcolith phase (solid) of Helicosphaera carteri (p. , Figs. 10C, D and Fig. 11A. Kleijne, 1991 S. confusus is now considered as the holococcolith phase (perforate) of Helicosphaera carteri (p. , Fig. 11B). ( The coccoliths are constructed of a rim and a cover which is centrally thick and has finger-like lateral protrusions which rest on the rim; the central part of the coccolith is hollow.

Syracolithus dalmaticus
Syracolithus dalmaticus resembles S. confusus, differing mainly in possessing hollow holococcoliths with real holes in the cover instead of having real laminoliths with superficial pits.
In the studied coccospheres were counted around of 45 coccoliths.

Zygosphaera marsilii
Body laminoliths with four concentric distal rows of crystallites, which are surmounted by a central structure of microcrystals, usually with the form of a transverse ridge. Circum-flagellar zygoform laminoliths have a high transverse ridge.

Species INCERTAE SEDIS
Holococcolithophore sp. 1 (coccoliths have two small pores in the proximal side) (Figs. 110A, B) Elliptical holococcoliths with a central protrusion surrounded by pores on the distal surface and two small pores aligned obliquely to the major axis in the proximal side; the basal plate seems to be solid.
Coccolithophore sp. 1 (affinity to Rhabdosphaeraceae?) (Figs. 110C,D) The coccosphere appears to have three types of coccoliths: a) long elliptical with laterally flattened protrusion; b) long elliptical with whaleback protrusion; c) broadly elliptical with tall cylindrical protrusion. Each type of coccolith shows a highly variety of sizes and have affinities with Algirosphaera and Cyrtosphaera coccoliths. This new species differs, however, from Algirosphaera and Cyrtosphaera because its elements are somewhat structureless (e.g. it is not possible to see radial laths or a differentiated rim).
Coccolithophore sp. 2 (affinity to Syracosphaera?) (Figs. 111A) The single collapsed specimen has coccoliths which slightly resemble those of Syracosphaera, especially since certain coccoliths have a small central spine. This species differs from Syracosphaera, however, in not having clear radial laths and in having a covered rim.

Coccolithophore sp. 3 (affinity to
Sphaerocalyptra?) (Fig. 111B) Very small calyptrolith-like coccoliths consisting of a ring with a bridge forming the cover of the calyptrolith; certain coccoliths are larger and appear to be circum-flagellar calyptroliths (upper rigth). These forms appear to be closer to calyptroliths than zygoliths, which are the typical forms having a bridge. They differ from the holococcoliths, however, in not having clear crystallites. Observation at a higher magnification is necessary to determine whether or not these actually are holococcoliths.
The two studied specimens have around 72 and 77 coccoliths.
Unidentified sp. no. 1 (Fig. 111C) Specimens that appear to have an external alveolate theca, but under high magnification it is sometimes possible to distinguish individual pieces composing this theca which could be compared to small coccoliths.
The three studied specimens have 456 to 896 small pieces (coccoliths?).
Unidentified sp. no. 2 ( Fig. 111D) This specimen presents a hard theca composed of pieces, which, if made by calcium compounds, might be related to the genus Papposphaera. In distal view, these structures resemble four pointed stars and are clearly variable in shape; the stars seem to be central structures attached to a basal ring with cross bars.