CORBULA. 215 



Corbula truncata, Sowerby, 1836. Plate XXXIV, figs. 17—22. 



1836. Corbula truncata, J. de C. Sowerby. Trans. Geol. Soc, ser. 2, vol. iv, 



pp. 240, 341, pi. xvi, fig. 8. 

 1850. A. d'Orbigny. Prodr. de Pal., vol. ii, p. 160. 



1854. J. Morris. Cat. Brit. Foss., ed. 2, p. 196. 



1868. A. Briart and F. L. Cornet. Meule de Bracquegnies 



(Mem. cour. et Mem. des Sav. etrangers, vol. xxxiv), 

 p. 81, pi. vi, figs. 13—15. 

 1870. F. Stoliczka. Palaeont. Inclica, Cret. Fauna S. India, 



vol. iii, p. 40. 

 (?) 1895. cf. — E. Tiessen. Zeitschr. d. deutsch. geol. Gesellsch., 



vol. xlvii, p. 485. 



Non 1846. A. d'Orbigny. Pal. Franc. Terr. Cret., vol. iii, p. 461, 



pi. ccclxxxviii, figs. 18 — 20 (? C. 

 Oold/ussiana, Matheron). 



Description. — Shell subquadrate or subtriangular, elongate, rounded, moderately 

 convex, inequilateral, slightly inequi valve, considerably longer than high. Anterior 

 margin well rounded. Ventral margin slightly convex, its posterior part bending 

 upwards. Posterior margin obliquely truncated, forming an acute angle with the 

 ventral margin and an obtuse angle with the dorsal margin. Umbones broad, 

 with a carina extending to the postero-ventral angle and cutting off a flattened or 

 concave postero-dorsal area. Ornamentation consists of numerous fine, concentric 

 ribs which are continued on to the postero-dorsal area. 



Measurements : 



(i) (2) (3) (i) 



Length ... 9 8*5 8 7*5 mm. 



Height ... 6-5 6 575 5 



(1 — 4) Blackdown. 



Affinities. — This species is less elongate than G. truncata, d'Orbigny, and is 

 also distinguished by its concentric ornamentation. It differs from G. lineata, 

 Muller, 1 in the greater obliquity of the posterior margin and in the more numerous 

 concentric ribs. 



Type. — From Blackdown, in the Bristol Museum. 



Distribution. — Upper Greensand (zone of Schlosnbachia, rostrata) of Blackdown. 



1 Holzapfel, "Die Mollusk. Aachen. Kreide " (' Palaeontographica,' vol. xxxv, 1889), p. 146, pi. x, 

 fis?s. 16—19. 



