. Bulletin of the British Museum (Natural History), Geology. 300 MID-TERTIARY CYTHERETTINAE In the hinge of the left valve, the antero-ventral lobe is weakly developed, leaving the anterior socket almost open ventrally; the antero-dorsal lobe is flat to lobate and small; the antero-median tooth is large; the postero-median swelling small. In the right valve the anterior tooth is large and the posterior tooth is slightly reniform. The anterior indentation of the inner margin is narrow; the ventral deep and prominent; and the posterior broad, but deep. The median segment is almost flat; the post
. Bulletin of the British Museum (Natural History), Geology. 300 MID-TERTIARY CYTHERETTINAE In the hinge of the left valve, the antero-ventral lobe is weakly developed, leaving the anterior socket almost open ventrally; the antero-dorsal lobe is flat to lobate and small; the antero-median tooth is large; the postero-median swelling small. In the right valve the anterior tooth is large and the posterior tooth is slightly reniform. The anterior indentation of the inner margin is narrow; the ventral deep and prominent; and the posterior broad, but deep. The median segment is almost flat; the posterior segment is steeper, but not very pronounced. The muscle scars are normal, the two ventral scars being close together. They are situated in a slight pit. The selvage runs along the anterior margin of both valves, so there is no anterior flange groove. A ventral flange groove is well developed, as well as a small posterior one. A very weak list is present along the ventral and posterior Fig. 14. Cytheretta cavita sp. nov.; female right valve; X75. Dimensions: L H W L/H Female 0-87 0-55 0-43 1-58 Male 0-93 0-53 0-41 175 Discussion: This differs from other smooth Cytheretta species such as C. rhenana Triebel by its shape and the presence of the posterior dimples. It shows a very close relationship to C. eocaenica, but lacks the longitudinal rows of pits of the latter. Cytheretta cellulosa sp. nov. (PL 9, figs 1-4, 6, 7) Derivation of name : Latin—cellulosus, full of little cells, referring to the orna- mentation. Diagnosis: A species of Cytheretta with 13 rows of pits which converge at the posterior; dorsal area is smooth. Holotype: Io 3859, a female left valve. Paratypes: Io 3860-63. Material : Eight valves and carapaces from the type Auversian; fourteen valves and carapaces from Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrati
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