L56 CRETACEOUS LAMELLIBRANCHIA. 



ventra] slope. The ribs are more numerous than in Lucina. Nereis, d'Orbigny, ] 

 from the Cenomanian. 



Distribution. — Upper Greensand (zone of Schlcenbachia rostrata) of Blackdown. 

 Upper Greensand near Lyme Regis. 



Ltjcina pisum, Sowerby, 1836. Plate XXIV, figs. 10— 19. 



1830. Lucina tisum, /. de C. Sowerby. Trans. Geol. Soc., ser. 2, vul. iv, pp. 241, 



341, pi. xvi, fig. 14. 

 1850. A. d'Orbigny. Prodr. de Pal., vol. ii, p. 162. 



1854. /. Morris. Cat, Brit, Foss., ed. 2, p. 208. 



1871. F. StoliczJca. Palseont. Indica, Cret. Fauna S. India, vol. 



iii, p. 252. 



Non 1844. A. d'Orbigny. Pal. Franc. Terr. Cret., vol. iii, pi. eclxxxi, 



figs. 3 — 5 (L. Cornueliana, p. 116). 

 ? — 1868. A. Briart and F. L. Cornet. Meule de Bracquegnies (Mem. 



cour. et Mem. des Sav. etrangers, vol. 

 xxxiv), p. 69, pi. viii, figs. 18 — 21. 



Description. — Shell small, very convex, with nearly circular outline, slightly 

 inequilateral ; length and height riearly equal. Anterior and ventral margins 

 forming a regular curve ; posterior margin slightly truncated, forming an obtuse 

 angle with the postero-dorsal margin, Umbones rather large. Lunule ovate, 

 broad, depressed. Escutcheon indistinctly limited. Ornamentation consists of 

 concentric ribs, with growth-rings at intervals. 



Measurements .- 



(1) (2) (3) 



Length . 5 . 4*5 . 4 mm. 



Height . 4-9 4"3 . 4 „ 



Thickness . 3-5 . 3 . 2*9 „ 



(1—3) Blackdown. 

 TLemarlcs. — The form referred to L. pisum by Briart and Cornet is much larger 

 than the English examples of that species, and also differs in its relatively longer 

 and more compressed shell. 



Type. — From Blackdown ; in the Bristol Museum. 



Distribution. — Upper Greensand (zone of Schlosnbachia rostra to) of Blackdown. 



i 'Prodr.de Pal.,' vol. ii (1850), p. 162. Gueranger, 'Album Paleont. de la Sarthe' (1867), 

 p. 12, pi. xv, fig. 15. The hinge figured by Gueranger does not agree with Lucina. Stoliezka suggests 

 that this species belongs to Cyprimeria, see ' Palaeont. Iudica, Cret. Fauna S. India' (1871), 

 pp. 164, 253. 



