. Bulletin of the British Museum (Natural History), Geology. MIDDLEJURASSICOSTRACOD\ in transitory between Progonocythere Sylvester-Bradley (1948 : 189) and Marslatourella Malz (1959: 19). This is suggested by the general similarity of carapace outline, muscle scars and radial pore canals present in all three. Progonocythere has a strong entomodont hinge and only a faint suggestion of an eye swelling. In Marslatourella the hinge is antimerodont and a strong eye tubercle is developed. At the same time prominent ventro-lateral outgrowths of the carapace occur. Malzia possesses a hinge which can
. Bulletin of the British Museum (Natural History), Geology. MIDDLEJURASSICOSTRACOD\ in transitory between Progonocythere Sylvester-Bradley (1948 : 189) and Marslatourella Malz (1959: 19). This is suggested by the general similarity of carapace outline, muscle scars and radial pore canals present in all three. Progonocythere has a strong entomodont hinge and only a faint suggestion of an eye swelling. In Marslatourella the hinge is antimerodont and a strong eye tubercle is developed. At the same time prominent ventro-lateral outgrowths of the carapace occur. Malzia possesses a hinge which can be considered as entomodont, a low eye swelling and ventro-lateral outgrowths of the carapace. It appears, therefore, that the development of ventro- lateral outgrowths coupled with a change from an entomodont to an antimerodont hinge and the development of an eye tubercle results in the appearance in the Bathonian of the genus Marslatoiirella. This evolutionary series commences in the Bajocian with the genus Progonocythere an offshoot of which produces Malzia. This second lineage then continues giving rise to Marslatourella. The genus Marslatourella described by Malz from the Bathonian of France (Mars-la Tour and Boulonnais) and Germany (Eichberg) is also common in the Bathonian sediments of England. Species of this genus will be described in forthcoming pub- lications. Malzia bicarinata sp. nov. (PI. 9, figs. 5-8 ; PL 10, figs. 1-3 ; Text-figs. 11-14) Diagnosis. Malzia with two, short, well developed ventro-lateral keels. Internal details as for genus. HoLOTYPE. , bed 9, Ravenscar section. Paratypes. , beds 7 and 8, Ravenscar and bed 7, Bloody Beck. J. 12 Fig. II. Muscle scars. Malzia bicarinata sp. nov. Paratype, , approx. X290. Figs. 12-13. Dorsal and left views, complete carapace Malzia bicarinata sp. nov. Holotype, , approx. Please note that these images are extracted from scanned page images that may have been digitally enhanced for
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