CORBULA. 211 



18t)5. IsooAKUiA? ANUULATA, F.J. Pictt't and G. Cuinpiche. Foss. Terr. Crct. Ste. 



Croix (Mater. Pal. Suisse, 

 ser. 4), p. 240. 

 1871. IsocARDiA ANGULATA, F. Staliczku. PaloGout. luJica, Cret. Fauua S. luclia, 



vol. iii, p. 194. 

 1877. IsocARDiA ? ANGULATA, &'. iy'////)(. Zeitsclir. d. deutscli. geol. Gesellscb., 



vol. .xxix, p. 241. 

 1889. IsocAKDiA ANGULATA, G. W. LampliKjli. Quart. Jo\u-u. Geol. Soc, vol. xlv, 



p. 616. 

 1900. — — A. WoUemann. Die Biv. u. Gastrop. d. deutscli. u. 



bolliiud. Neocoms (Abliaudl. d. k. 

 preussiscli. geol. Laud., N. P., pt. 

 31), p. 114. 



1905. CoKBULA (Isocardia) AviovhAiA, E. Harhort. Fauua d. Seliaiunberg-Lippe- 



scbeu Kreidemulde (Ibid., 

 pt. 45), p. 81. 



1906. Isocardia angulata, A. WoUemann. Die Biv. u. Gastrop. nord-deutsch. 



Gaults (Jabrb. d. k. preussiscb. 

 geol. Laud., filr 1906, vol. xxvii), 

 p. 277. 



Descrijjtioii. — Shell witli 8ul)-(]uadrate outline, rounded, occasionally sub- 

 triangular, very convex, equivalve, more or less considerably inequilateral ; length 

 greater than height. Anterior part produced, rounded ; ventral margin slightly 

 curved ; posterior margin truncate, slightly convex, somewhat oblique, forming 

 angles with the ventral and dorsal margins. Postero-dorsal margin sloping 

 ventrally. Umbones moderately large, curved inward and more or less considerably 

 forward, with a carina extending to the postero-ventral angle, cutting off a large, 

 flattened postero-dor.sal area. The part of the valve in front uf the carina is 

 regularly convex. Lunular region depressed. 



Ornamentation consists of fine concentric striae. 

 Measarctiioits : 



(3) (-4) 



6-2 . G 

 5-0 . 5 



(1 — 7) Speetou. 



Ajjiiiitii'.-i. — This species shows some resemblance to C. tjatilliiui (see p. 21 1), but 

 is more nearly (juadrate in outline, relatively longer, of larger size, and without 

 distinct ribs. 



G. aiKjulata is fairly common in the Speeton Clay, but no specimen showing the 

 hinge appears to have l)een found, so that the generic position assigned to this 

 species by Phillips was presumal)ly based on the external character of the shell. 

 Pictet and Campiche thought that it probably belonged to Ci/jn-iiui. WoUemann 

 states that it is most likely a Curiula, and Harbort, who has seen the hinge, 



