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Morphological Affinities in Ostracoda, Misleading and Revealing
Morphological Mnities in Ostracoda, Misleading and Revealing H m z MALZ
Forschungsinstitut Senckenberg, Frankfurt am Main, F.R. Germany
ABSTRACT In many cases the outline of an ostracod carapace is a first criterion for its generic determination. However, more characteristics are needed for qualified generic assignment, as shape may turn out to be a very misleading feature. For example, were it not for the bairdiid muscle scars, Pterobairdia could easily be mistaken for a Cytheropteron. Similarly a Bairdiu-shaped ostracod may not necessarily bear any relationship to Buirdia or to any of its allied genera. Therefore Buirdiacythere is introduced as a new subgeneric taxon of Schuleridea and grouped within Cytheridae, Cytherideinae, Schulerideini. The new taxon which by its name alludes to the genera Bairdia and Cythere is characterized by its bairdiid shape, but proves cytherid by its muscle scars. Schuleridea (Buirdiacythere) is closely related to a group of Bathonian ostracods which is included in Schuleridea (Eoschuleridea)that precedes the Upper Jurassic to Cretaceous Schulerideu (Schuleridea).Beside the phylogenetic development of Schulerideu (Eoschuleridea) to Schuleridea (Schuleridea) a local, perhaps an endemic, development simultaneously produced Schulerideu (Bairdiacythere)as an ecologically favoured offshoot of Schulerideu (Eoschuleridea). Rather than raising Schuleridea (Eoschuleridea) to generic rank in order to point out its close relationship with Bairdiacythere as a subgenus of it, the subgeneric status for both Schuleridea (Eoschuleridea) and Schuleridea (Bairdiacythere) is favoured. This taxonomical valuation is paralleled by the Neogene Schuleridea (Amphischuleridea) which comes closer to Schuleridea (Aequacytherideu) rather than to Schuleridea (Schulerideu).
INTRODUCTION The Old Cement Works quarry at Kirtlington in Oxfordshirehas proved to be a locality extremely rich in Upper Bathonian ostracod faunas, both in species and specimens. In the inventory of ostracod species listed by Ware and Whatley (1980) from that locality a total of 92 speces is contained, 59 of which are determined to the specific level leaving the rest to cf. and aff. determinations or to open nomenclature. By their description of a farther 12 species, Ware and Whatley increased the number of taxa to more than 70 known species from Kirtlington Quarry, mainly marine, but Borne also indicative for freshwater. Among the numerous species there is a very remarkable from which is reminiscent of a bairdiid in its outline and shape. However, its muscle scars prove it to be a cytherid. Since the species occurs in great numbers, it cannot be overlooked in the various samples from the Kirtlington Forest Mar57
58 H. MALZ
ble. However, since the species has not been mentioned in the literature before, it must have been misidentified (determined perhaps as Bairdia hilda), or left under open nomenclature (? which). As regards the internal features of the new Bairdia-like cytherid, its close relationship to species grouped within Schuleridea (Eoschuleridea) Bate, 1967 can be ascertained. However, from differences in outline and hinge structure a separate status is proposed, namely Schuleridea (Bairdiacythere) subg. nov. By the introduction of a new subgeneric unit the “aspects of the Subfamily Schulerideinae” (Neale, 1982: 181) become even more complex. On the other hand, this complexity proves in fact a skilled and useful solution in taxonomy which is really “as much an art as a science”.
SYSTEMATIC PART Family CYTHERIDAE Baird, 1850 Subfamily CYTHERIDEINAE Sars, 1925 Tribe SCHULERJDEINI Mandelstam, 1959 Remarks.-With reference to Neale (1982: 180) “the Schulerideinae is a practical grouping of convenience”. In correspondance with that valuation the two equivalent tribes Schulerideini and Apatocytherini Grundel, 1976 likewise and sufficiently validate Neale’s conception of Schulerideinae. This devaluation of Schulerideinaeto infrasubfamilia rank stands, it is true, against the opposite version approached by Bate (1967) and followed by Kollmann (1971) who raised Schula rideinae to familia rank. However, since “there has been a veritable explosion of ostracod genera in the last two decades” (Neale, 1982: 185), shifting to higher categories neither includes better possibilities for the determination and classification of genera nor does it render any help for a better understanding of ostracod phylogeny. On the contrary, since shifting to higher categories does not keep in step with the number of available features in an ostracod carapace, generic determination becomes more and more obscure by less and less features. Thus, for very practical reasons the determination of an ostracod as belonging to the family Cytheridae gives as much in formation as its determination as a cytheracean or as a cytherocopine. This pragmatic point of view is approached also by the “zoological systematics” presented by Hartmann (1975: 724) who recognizes Schulerideini within Cytherideinae of the family Cytheridae. 7
Genus SCHULERIDEA Swartz and Swain, 1946 Type species.-Schuleridea acuminata Swartz and Swain, 1946. Subgenus SCHULERIDEA (BAIRDIACYTHBRE) subg. nov. Type species.-Schuleridea (Bairdiacythere) bairdiaformis sp. nov. Name.-With reference to the Bairdia-like outline and the cytherid relationship. Diagnosis.-A subgenus of Schulerideawithout an eye swelling, but with a faintly marked ocular sinus below the anterior part of hinge in the RV. Carapace sub-ovate in side view with a concave (Bairdia-like) posterodorsal break behind which the posterior end is pointed, more so in the smaller
KATE 1-All
specimens are from the Upper Bathonian Forest Marble of the Old Cement Works quarry at Kirtlington, Oxfordshire (Mz 72/1967). Measurements (in brackets) refer to length of specimens in pm. LV = left valve, RV = right valve, C = carapace. Magnification x 84, unless stated otherwise. Figs. 1-2. Schuleridea (Eoschulerideu) buthonicu Bate, 1967. 1. Female C (710), right lateral.-Xe 12933; 2. Female LV (730), internal lateral.-Xe 12933. Figs. 3-5. Schuleridea (Eoschulerideu) trigonulis (Jones, 1884). 3. Female C (730), right lateral.-Xe 12936; 4. Female LV (720). internal lateral.-Xe 12936; 5. Female C (680), dorsal.-Xe 12937. Figs. 6-9. Schuleridea (Buirdiucythere) buirdiuformis sp. nov. 6. Female C (740), right lateral.-Xe 12920; 7. Male C (740). dorsal.-Xe 12921 ; 8. Female LV (740), a) internal lateral, b) hinge, X 165.-Xe 12922; 9. Female C (700), ventral.-Xe 12923.
Morphological Afinities in Ostracoda 61
RV than in the overlapping LV. Tripartite hinge short, restricted to mid-third of valve length, of
the paleomerodont type and with an accommodation groove above the central part in the LV. Duplicature moderately broad, with about 25 radial pore canals anteriorly and 9 posteriorly. Muscle scars correspond to the cytherid type with four adductors, one frontal and two separate mandibular scars. Description.-As for the type species. Relationship.-The subgenus is closely related to Schuleridea (Eoschulerideu) Bate, 1967 with which it has in common the cytherid type of muscle scars and the development of the marginal zone, but differs from it in the Buirdiu-like shape and the short compressed hinge of the paleomerodont type. Within the Schulerideini similar indentations of the outline occur in Pseudocytherideu Schneider, 1949 and in Schuleridea (Amphischulerideu)Kollmann, 1971. However, in both taxa (or is it only one ?) the carapace is incurved posteroventrally. Stratigraphic range.-Middle Jurassic (Upper Bathonian). Distribution.-Known from the Oxfordshire area only.-Although many Bathonian localities are known to me by their ostracod faunas I did not come across any form similar to the species described below. Therefore I suppose that the species developed as a very local element proving adaption to endemism. Biotope.-The biotope in which the species occurs is dominated by marine ostracods, yet some indicators for freshwater are present, for instance Theriosynoecum kirtlingtonense Bate, 1965 and Limnocythere ceratina Ware and Whatley, 1980. The mixture of ostracods from different habitats has been subject to various explanations (referred to by Ware and Whatley, 1980). These explanations range from reworked freshwater deposits in a marine environment via autochthonous brackish water layers to an interfingering of freshwater and marine sediments in the tidal area of a river system. From the rich material at my disposal I gathered some information which may turn out useful for an explanation: The preservation of the marine species varies widely and ranges from very well to poorly preserved specimens, whereas that of the freshwater species is quite excellent. Couldn’t this mixture point to a freshwater pool filled by reworked marine sediments? SCHULERIDEA (BAIRDIACYTHERE) BAIRDIAFORMIS sp. nov. (Pl. 1, figs. 6-9; P1. 2, figs. 10-17) Name.-With reference to the Bairdia-like outline. Ho1otype.-Male carapace, P1. 2, fig. 17; SMF Xe 12919. Type locality and horizon.-Old Cement Works quarry at Kirtlington, Oxfordshire, England. Upper Bathonian, Forest Marble. Paratypes.-More than 150 carapaces and valves: SMF Xe 12920-12932. Diagnosis.-As for the monotypic subgenus. Measurements (dimensions in ,urn).-The size of the adult specimens covers a wide range, from length 630/height 420 to length 78O/height 500. Presumably the smaller specimens (length 630-740) represent females, whereas the larger specimens (length 690-780) represent males. As there is a large F U T E 2-All specimens are from the Upper Bathonian Forest Marble of the Old Cement Works quarry at Kirtlington, Oxfordshire (Mz 72/1967). Measurements (in brackets) refer to length of specimens in pm. LV = left valve, RV = right valve, C = carapace. Magnification x 83, unless stated otherwise. Figs. 10-17. Schuleridea (Buirdiacythere) bairdiuformis sp. nov. 10. Female C (720), dorsal (slightly tilted to show overlap).-Xe 12924; 11. Male RV (750), a) internal lateral, b) hinge, x 165, c) muscle scars, x 165 (4 adductors, 1 frontal, and 2 mandibulars).-Xe 12922; 12. Male RV (750), dorsal.-Xe 12924; 13. Male LV (690), a) internal lateral, b) hinge, x 165.-Xe 12920; 14. Male RV (740), internal lateral.-Xe 12921; 15. Female LV (700), internal lateral.-Xe 12923; 16. Female C (740), right lateral.-Xe 12925; 17. Male C (780), holotype, right lateral.-Xe 12919.
62 H. MALZ
overlap in size, sexual dimorphism remains somewhat uncertain. Therefore, specimens that are more pointed posteriorly (Pl. 2, figs. 13, 17) are regarded as males, the less pointed specimens (Pl. 2, figs. 15, 16) are taken to represent the females.-In some juvenile specimens (lengthd560) a very narrow duplicature is present and the Bairdia-like posterodorsal break is but faintly developed. Description.-Carapace sub-ovate in side view with a Bairdia-like concave break in the posterodorsal part, below which the posterior end is more pointed in the RV than in the LV. Larger LV highly arched mid-dorsally overlapping the smaller RV along the entire margin, especially in the posterodorsal break. Greatest length below mid-point, greatest height at about mid-length. Carapace oval in dorsal view with greatest width median. Surface smooth, finely punctate by widely spaced openings of lateral pore canals. Hinge short, restricted to mid-third of dorsal margin, tripartite and of the paleomerodont type. In the LV the anterior part of the hinge is developed as a deep. oval, loculate trough which is framed proximally by a torose lip. Medially there is a short, shallow, narrow furrow connecting the terminal hinge parts. The posterior part consists of a deeply incised, oval, loculate socket without any proximal frame. Above the median hinge part a distinct accommodation groove is visible, even in lateral right side views of closed carapaces. Inner margin and line of concrescence coincide; duplicature moderately broad anteriorly, rather narrow posteriorly. Radial pore canals densely spaced, slightly curved, about 25 anteriorly and 9 posteriorly, bent to openings on the sub-peripheral lateral exterior, but not terminating marginally. As a result of overlap, the terminal ends of the LV are rims projecting over the RV; proximal to the rounded rim the smaller RV rests against a subperipheral zone marked by fine striae in the LV; P1.l, fig. 8a, P1.2, figs. 13a,b, 15. The vertical row of 4 adductor scars is slightly curved behind a prominent oval frontal scar. Two mandibular scars are positioned anteroventrally and ventrally. Relationship.-Schuleridea (Bairdiacythere) bairdiaformis sp. nov. is closely related to a group of species assigned to Schuleridea (Eoschuleridea) occurring in the same samples from the Kirtlington quarry (Pl. 1, figs. 1-5), but differs from all the others by its bairdioid shape, its compressed hinge, and the torose lip supporting the anterior socket. Occurrence.-So far the species has been found in several samples from the type locality.
REFERENCES 1967. The Bathonian Upper Estuarine Series of Eastern England. Part I: Ostracoda. Bull. Brit. Mus. (Natural Hist.), Geol., 14 (2), 23-66, 22 pls. HARTMANN, 0. 1975. Ostracoda. In Bronns Klassen und Ordnungen des Tierreichs, 5, Bd. (Arthropoda), I . Abt. (Crustacea), 2. Buch, I V Teil, 1-4, Lieferung, 1-786, Akademische Verlagsgesellschaft, Leipzig. KOLLMANN, K. 1971. Die Ostracoden der Eggenburger Schichtengruppe Niederosterreichs. In STEININGER, F. and SENES, J. Chronostratigraphie und Neostratotypen; MiozAn der zentralen Paratethys, 2, 605-717, 16 pls. NEALE, J.W. 1982. Aspects of the Subfamily Schulerideinae. In BATE, R.H., ROBINSON, E. and SHEPPARD, L.M. (eds.), Fossil and Recent Ostracods, 178-192. Ellis Horwood Ltd., Chichester. WARE, M., and WHATLEY,R. 1980. New genera and species of Ostracoda from the Bathonian of Oxfordshire, England. Rev. esp. Micropaleontol., 12 (2), 199-230, 5 pls. BATE, R.H.
Forschungsinstitut Senckenberg, Frankfurt am Main, F.R. Germany
ABSTRACT In many cases the outline of an ostracod carapace is a first criterion for its generic determination. However, more characteristics are needed for qualified generic assignment, as shape may turn out to be a very misleading feature. For example, were it not for the bairdiid muscle scars, Pterobairdia could easily be mistaken for a Cytheropteron. Similarly a Bairdiu-shaped ostracod may not necessarily bear any relationship to Buirdia or to any of its allied genera. Therefore Buirdiacythere is introduced as a new subgeneric taxon of Schuleridea and grouped within Cytheridae, Cytherideinae, Schulerideini. The new taxon which by its name alludes to the genera Bairdia and Cythere is characterized by its bairdiid shape, but proves cytherid by its muscle scars. Schuleridea (Buirdiacythere) is closely related to a group of Bathonian ostracods which is included in Schuleridea (Eoschuleridea)that precedes the Upper Jurassic to Cretaceous Schulerideu (Schuleridea).Beside the phylogenetic development of Schulerideu (Eoschuleridea) to Schuleridea (Schuleridea) a local, perhaps an endemic, development simultaneously produced Schulerideu (Bairdiacythere)as an ecologically favoured offshoot of Schulerideu (Eoschuleridea). Rather than raising Schuleridea (Eoschuleridea) to generic rank in order to point out its close relationship with Bairdiacythere as a subgenus of it, the subgeneric status for both Schuleridea (Eoschuleridea) and Schuleridea (Bairdiacythere) is favoured. This taxonomical valuation is paralleled by the Neogene Schuleridea (Amphischuleridea) which comes closer to Schuleridea (Aequacytherideu) rather than to Schuleridea (Schulerideu).
INTRODUCTION The Old Cement Works quarry at Kirtlington in Oxfordshirehas proved to be a locality extremely rich in Upper Bathonian ostracod faunas, both in species and specimens. In the inventory of ostracod species listed by Ware and Whatley (1980) from that locality a total of 92 speces is contained, 59 of which are determined to the specific level leaving the rest to cf. and aff. determinations or to open nomenclature. By their description of a farther 12 species, Ware and Whatley increased the number of taxa to more than 70 known species from Kirtlington Quarry, mainly marine, but Borne also indicative for freshwater. Among the numerous species there is a very remarkable from which is reminiscent of a bairdiid in its outline and shape. However, its muscle scars prove it to be a cytherid. Since the species occurs in great numbers, it cannot be overlooked in the various samples from the Kirtlington Forest Mar57
58 H. MALZ
ble. However, since the species has not been mentioned in the literature before, it must have been misidentified (determined perhaps as Bairdia hilda), or left under open nomenclature (? which). As regards the internal features of the new Bairdia-like cytherid, its close relationship to species grouped within Schuleridea (Eoschuleridea) Bate, 1967 can be ascertained. However, from differences in outline and hinge structure a separate status is proposed, namely Schuleridea (Bairdiacythere) subg. nov. By the introduction of a new subgeneric unit the “aspects of the Subfamily Schulerideinae” (Neale, 1982: 181) become even more complex. On the other hand, this complexity proves in fact a skilled and useful solution in taxonomy which is really “as much an art as a science”.
SYSTEMATIC PART Family CYTHERIDAE Baird, 1850 Subfamily CYTHERIDEINAE Sars, 1925 Tribe SCHULERJDEINI Mandelstam, 1959 Remarks.-With reference to Neale (1982: 180) “the Schulerideinae is a practical grouping of convenience”. In correspondance with that valuation the two equivalent tribes Schulerideini and Apatocytherini Grundel, 1976 likewise and sufficiently validate Neale’s conception of Schulerideinae. This devaluation of Schulerideinaeto infrasubfamilia rank stands, it is true, against the opposite version approached by Bate (1967) and followed by Kollmann (1971) who raised Schula rideinae to familia rank. However, since “there has been a veritable explosion of ostracod genera in the last two decades” (Neale, 1982: 185), shifting to higher categories neither includes better possibilities for the determination and classification of genera nor does it render any help for a better understanding of ostracod phylogeny. On the contrary, since shifting to higher categories does not keep in step with the number of available features in an ostracod carapace, generic determination becomes more and more obscure by less and less features. Thus, for very practical reasons the determination of an ostracod as belonging to the family Cytheridae gives as much in formation as its determination as a cytheracean or as a cytherocopine. This pragmatic point of view is approached also by the “zoological systematics” presented by Hartmann (1975: 724) who recognizes Schulerideini within Cytherideinae of the family Cytheridae. 7
Genus SCHULERIDEA Swartz and Swain, 1946 Type species.-Schuleridea acuminata Swartz and Swain, 1946. Subgenus SCHULERIDEA (BAIRDIACYTHBRE) subg. nov. Type species.-Schuleridea (Bairdiacythere) bairdiaformis sp. nov. Name.-With reference to the Bairdia-like outline and the cytherid relationship. Diagnosis.-A subgenus of Schulerideawithout an eye swelling, but with a faintly marked ocular sinus below the anterior part of hinge in the RV. Carapace sub-ovate in side view with a concave (Bairdia-like) posterodorsal break behind which the posterior end is pointed, more so in the smaller
KATE 1-All
specimens are from the Upper Bathonian Forest Marble of the Old Cement Works quarry at Kirtlington, Oxfordshire (Mz 72/1967). Measurements (in brackets) refer to length of specimens in pm. LV = left valve, RV = right valve, C = carapace. Magnification x 84, unless stated otherwise. Figs. 1-2. Schuleridea (Eoschulerideu) buthonicu Bate, 1967. 1. Female C (710), right lateral.-Xe 12933; 2. Female LV (730), internal lateral.-Xe 12933. Figs. 3-5. Schuleridea (Eoschulerideu) trigonulis (Jones, 1884). 3. Female C (730), right lateral.-Xe 12936; 4. Female LV (720). internal lateral.-Xe 12936; 5. Female C (680), dorsal.-Xe 12937. Figs. 6-9. Schuleridea (Buirdiucythere) buirdiuformis sp. nov. 6. Female C (740), right lateral.-Xe 12920; 7. Male C (740). dorsal.-Xe 12921 ; 8. Female LV (740), a) internal lateral, b) hinge, X 165.-Xe 12922; 9. Female C (700), ventral.-Xe 12923.
Morphological Afinities in Ostracoda 61
RV than in the overlapping LV. Tripartite hinge short, restricted to mid-third of valve length, of
the paleomerodont type and with an accommodation groove above the central part in the LV. Duplicature moderately broad, with about 25 radial pore canals anteriorly and 9 posteriorly. Muscle scars correspond to the cytherid type with four adductors, one frontal and two separate mandibular scars. Description.-As for the type species. Relationship.-The subgenus is closely related to Schuleridea (Eoschulerideu) Bate, 1967 with which it has in common the cytherid type of muscle scars and the development of the marginal zone, but differs from it in the Buirdiu-like shape and the short compressed hinge of the paleomerodont type. Within the Schulerideini similar indentations of the outline occur in Pseudocytherideu Schneider, 1949 and in Schuleridea (Amphischulerideu)Kollmann, 1971. However, in both taxa (or is it only one ?) the carapace is incurved posteroventrally. Stratigraphic range.-Middle Jurassic (Upper Bathonian). Distribution.-Known from the Oxfordshire area only.-Although many Bathonian localities are known to me by their ostracod faunas I did not come across any form similar to the species described below. Therefore I suppose that the species developed as a very local element proving adaption to endemism. Biotope.-The biotope in which the species occurs is dominated by marine ostracods, yet some indicators for freshwater are present, for instance Theriosynoecum kirtlingtonense Bate, 1965 and Limnocythere ceratina Ware and Whatley, 1980. The mixture of ostracods from different habitats has been subject to various explanations (referred to by Ware and Whatley, 1980). These explanations range from reworked freshwater deposits in a marine environment via autochthonous brackish water layers to an interfingering of freshwater and marine sediments in the tidal area of a river system. From the rich material at my disposal I gathered some information which may turn out useful for an explanation: The preservation of the marine species varies widely and ranges from very well to poorly preserved specimens, whereas that of the freshwater species is quite excellent. Couldn’t this mixture point to a freshwater pool filled by reworked marine sediments? SCHULERIDEA (BAIRDIACYTHERE) BAIRDIAFORMIS sp. nov. (Pl. 1, figs. 6-9; P1. 2, figs. 10-17) Name.-With reference to the Bairdia-like outline. Ho1otype.-Male carapace, P1. 2, fig. 17; SMF Xe 12919. Type locality and horizon.-Old Cement Works quarry at Kirtlington, Oxfordshire, England. Upper Bathonian, Forest Marble. Paratypes.-More than 150 carapaces and valves: SMF Xe 12920-12932. Diagnosis.-As for the monotypic subgenus. Measurements (dimensions in ,urn).-The size of the adult specimens covers a wide range, from length 630/height 420 to length 78O/height 500. Presumably the smaller specimens (length 630-740) represent females, whereas the larger specimens (length 690-780) represent males. As there is a large F U T E 2-All specimens are from the Upper Bathonian Forest Marble of the Old Cement Works quarry at Kirtlington, Oxfordshire (Mz 72/1967). Measurements (in brackets) refer to length of specimens in pm. LV = left valve, RV = right valve, C = carapace. Magnification x 83, unless stated otherwise. Figs. 10-17. Schuleridea (Buirdiacythere) bairdiuformis sp. nov. 10. Female C (720), dorsal (slightly tilted to show overlap).-Xe 12924; 11. Male RV (750), a) internal lateral, b) hinge, x 165, c) muscle scars, x 165 (4 adductors, 1 frontal, and 2 mandibulars).-Xe 12922; 12. Male RV (750), dorsal.-Xe 12924; 13. Male LV (690), a) internal lateral, b) hinge, x 165.-Xe 12920; 14. Male RV (740), internal lateral.-Xe 12921; 15. Female LV (700), internal lateral.-Xe 12923; 16. Female C (740), right lateral.-Xe 12925; 17. Male C (780), holotype, right lateral.-Xe 12919.
62 H. MALZ
overlap in size, sexual dimorphism remains somewhat uncertain. Therefore, specimens that are more pointed posteriorly (Pl. 2, figs. 13, 17) are regarded as males, the less pointed specimens (Pl. 2, figs. 15, 16) are taken to represent the females.-In some juvenile specimens (lengthd560) a very narrow duplicature is present and the Bairdia-like posterodorsal break is but faintly developed. Description.-Carapace sub-ovate in side view with a Bairdia-like concave break in the posterodorsal part, below which the posterior end is more pointed in the RV than in the LV. Larger LV highly arched mid-dorsally overlapping the smaller RV along the entire margin, especially in the posterodorsal break. Greatest length below mid-point, greatest height at about mid-length. Carapace oval in dorsal view with greatest width median. Surface smooth, finely punctate by widely spaced openings of lateral pore canals. Hinge short, restricted to mid-third of dorsal margin, tripartite and of the paleomerodont type. In the LV the anterior part of the hinge is developed as a deep. oval, loculate trough which is framed proximally by a torose lip. Medially there is a short, shallow, narrow furrow connecting the terminal hinge parts. The posterior part consists of a deeply incised, oval, loculate socket without any proximal frame. Above the median hinge part a distinct accommodation groove is visible, even in lateral right side views of closed carapaces. Inner margin and line of concrescence coincide; duplicature moderately broad anteriorly, rather narrow posteriorly. Radial pore canals densely spaced, slightly curved, about 25 anteriorly and 9 posteriorly, bent to openings on the sub-peripheral lateral exterior, but not terminating marginally. As a result of overlap, the terminal ends of the LV are rims projecting over the RV; proximal to the rounded rim the smaller RV rests against a subperipheral zone marked by fine striae in the LV; P1.l, fig. 8a, P1.2, figs. 13a,b, 15. The vertical row of 4 adductor scars is slightly curved behind a prominent oval frontal scar. Two mandibular scars are positioned anteroventrally and ventrally. Relationship.-Schuleridea (Bairdiacythere) bairdiaformis sp. nov. is closely related to a group of species assigned to Schuleridea (Eoschuleridea) occurring in the same samples from the Kirtlington quarry (Pl. 1, figs. 1-5), but differs from all the others by its bairdioid shape, its compressed hinge, and the torose lip supporting the anterior socket. Occurrence.-So far the species has been found in several samples from the type locality.
REFERENCES 1967. The Bathonian Upper Estuarine Series of Eastern England. Part I: Ostracoda. Bull. Brit. Mus. (Natural Hist.), Geol., 14 (2), 23-66, 22 pls. HARTMANN, 0. 1975. Ostracoda. In Bronns Klassen und Ordnungen des Tierreichs, 5, Bd. (Arthropoda), I . Abt. (Crustacea), 2. Buch, I V Teil, 1-4, Lieferung, 1-786, Akademische Verlagsgesellschaft, Leipzig. KOLLMANN, K. 1971. Die Ostracoden der Eggenburger Schichtengruppe Niederosterreichs. In STEININGER, F. and SENES, J. Chronostratigraphie und Neostratotypen; MiozAn der zentralen Paratethys, 2, 605-717, 16 pls. NEALE, J.W. 1982. Aspects of the Subfamily Schulerideinae. In BATE, R.H., ROBINSON, E. and SHEPPARD, L.M. (eds.), Fossil and Recent Ostracods, 178-192. Ellis Horwood Ltd., Chichester. WARE, M., and WHATLEY,R. 1980. New genera and species of Ostracoda from the Bathonian of Oxfordshire, England. Rev. esp. Micropaleontol., 12 (2), 199-230, 5 pls. BATE, R.H.