424 MOLLUSCA. CARDIADjE. Pholadomy^a. 



8. C. semigranulatum.-— Gibbose, transverse, subtriangular, longitudinally 

 striated, posterior side straight, longitudinally sulcated, and largely granu- 

 lated. — Sower. Min. Conch, t. cxliv London Clay. 



9. C. angustatum. — Transversely elongated, thin, rather depressed ; costae 

 twenty-seven, margin toothed ; retrally truncated, anteally rounded — Sower. 

 Min. Conch, t. cclxxxiii. f. 2 Crag. 



10. C. edulinum. — Nearly orbicular, convex, slightly oblique, thick ; costae 



eighteen, rugose ; slightly truncated retrally Sower. Min. Conch, t. cclxxxiii. 



1* 3 — Crag. 



1 1. C. turgidum. — Obovate, transverse, smooth, gibbose ; longitudinally 

 striated retrally; edge minutely toothed. — (Brander, 96.) — Sower. Min. 

 Conch, t. cccxlvi. f. 1. — London Clay. 



12. C. porulosum — Orbicular, retrally obscurely truncated, longitudinally 

 sulcated, with a row of erect, approximate spines united near their points, 

 alternating with each sulcus; sulci terminated by ligulate teeth. Var. 

 spines united through their whole length by a membrane, and their bases 

 sunk beneath the edges of the sulci — {Brander, 99.) — Sower. Min. Conch, 

 t. cccxlvi. f. 2 — London Clay. 



13. Cstriatulum. — Orbicular, convex, concentrically striated, posterior side 

 longitudinally striated, with a toothed edge — Sower. Min. Conch, t. Dliii. f. 1. 

 — In Lias. 



14. C. truncatum. — Transversely ovate, gibbose, smooth; posterior side 

 obliquely truncated, longitudinally sulcated; beaks small — (C. pectinalum, 

 Young, and Brit. Geol. York. 226. t. viii. f. 5.)— Sower. Min. Conch, t. Dliii. 

 f. 3. — In Lias. 



15. C. dissimile — Transversely obovate, gibbose, smooth ; posterior side 

 bounded by a small rib, longitudinally striated ; front rather straight — Sower. 

 Min. Conch, t. Dliii. f. 2. — Upper Oolite. 



16. C. decussatum — Cordiform antiquated, longitudinally ribbed, anterior 

 margin rounded ; posterior side a broad area raised in the middle ; length 

 and breadth nearly equal — Mant. Geol. 126. t. xxv. f. 3. 



Gen. rHOLADOMY^A.--" A transverse, thin, subhya- 

 line, ventricose shell ; the posterior portion short, rounded ; 

 the anterior more or less elongated and gaping ; hinge 

 composed of an elongated subtrigonal faveola, and a mar- 

 ginal plate in each valve, with a rather short external liga- 

 ment ; the muscular impressions two, indistinct ; the sinus 

 in the impression of the mantel large ; the umbones ap- 

 proximated.'" — Sowerbv. 



1. P. producta.— Transversely oblong, gibbose, with six or seven angular 



longitudinal ridges; produced side plain Sower. Min. Conch, t. cxcvii. f. 1. 



— Inferior Oolite. 



2. P. obtusa — Transversely obovate, recurved, gibbose, with from seven to 



ten longitudinal, nearly equal, tuberculated ridges Sotver. Min. Conch. 



I. cxcvii. f. 2 — Inferior Oolite. 



