80 CRETACEOUS LAMELLIBRANCHIA. 



1846. Gervilia al^formis, A. d'Orbigny. Pal. Prau9. Terr. Oct., vol. iii, p. 484, 



pi. cccxcv, figs. 1 — 3. 

 1850. — — d'Orbigny. Prodr. de Pal., vol. ii, p. 82. 



1852. Avicula Ehodani, F. J. Pictet and W. Boux. Moll. Foss. Gres verts de 



Geneve, p. 494, pi. xli, 

 fig. 2. 

 1854. Gervillia al^formis, J. Morris. Cat. Brit. Foss., ed. 2, p. 167. 



1 853. Gervilia aliformis, F. J. Pictet and E. Benevier. Foss. Terr. Aptien (Mater. 



Pal. Suisse, ser. 1), p. 

 120, pi. xviii, figs. 1, 2. 

 H. Coquand. Mou. Aptien de l'Espagne, p. 144. 

 I 869 - — F. J. Pictet and G. Campiclie. Foss. Terr. Crt't. Ste. 



Croix (Mater. Pal. Suisse, ser. 

 5), p. 86, pi. clvi, fig. 1. 

 1871. Gervillea — F. Stoliczha. Palseont. Indica, Cret. Fauna S. India, 



vol. iii, p. 399. 



Description. — Shell thick, large, much inflated, triangular or rhombic, oblique. 



1865. 



Fig. 9. — Gervillia alwformis (Sowerby). Lower Greensand (Crackers), Atherfield. Sedgwick Museum. 

 Dorsal view, showing the ligament area of the right valve. Natural size. 



Anterior parts of both valves more or less nearly vertical to the plane of the valves. 

 Around the byssal opening the marginal parts of the valves are sometimes concave. 

 Umbones near the anterior extremity. Hinge-area large with large ligament pits 

 — usually five or six. Numerous narrow transverse teeth. 



Left valve larger and more inflated than the right, with its umbo strongly 

 incurved. A very prominent, convex portion extends from the umbo to the 

 rounded postero-ventral extremity ; dorsally it bends anteriorly ; ventrally it has 

 a slight posterior curvature. This convex part is separated by a shallow depres- 



