270 



51. CYTHERIDEA TRAPEZOID ALIS, Tenjuem. 



PI. iv., figs. 1 a, b. 



Mim. Soc. GM., France, ser. 3, vol. iv., 1885, p. 31, pi. iv., 

 figs, 20 a, b, c. 



Straight on the dorsal margin, angular behind, with the 

 postero-ventral slope reaching into the middle of the ventral 

 margin, giving to the latter an obtuse angle. Both anterior 

 and posterior margins are lipped. Surface moderately convex, 

 smooth, but sparsely pitted ; and with two or three shallow 

 transverse sulci in the dorsal region. Hinge-line very long. 



Terquem's figures are not quite equal among themselves, but, 

 taking the average, we think that they are not unlike the form 

 here figured and described. 



One specimen ; Blue Fullers-earth Clay, Midford. 



52, CYTHERIDEA PER.SICA,* Sp. n. 



PI. iv., fig. 4, 



Roughly obovate, much resembling a coarsely marked peach- 

 stone, rounded in front, angular behind, and lipped at each ex- 

 tremity. A strong longitudinal keel is developed on the ventral 

 margin of the valve, and this is repeated, with less intensity, by 

 the raised ridges of the concentric reticulation on that region. 



Edge view (not drawn), compressed ovate, with apiculate ends. 

 Hinge ment, like that of pi. i., fig. 2. 



One specimen ; Blue Fullers-earth Clay, Midford. 



63. CYTHERIDEA BICARINATA, Sp. tl. 



PI. iv., figs. 5 a, b, c. 



Sub-obovate, obliquely rounded in front, angular and lipped 

 behind. Dorsal margin oblique, with a straight hinge-line, 

 which is tuberculate externally. The ventral region bears two 



* With reference to the stone of a peach. 



