CEASSIPEDES. 129 



COWET. A common name for shells of the genus Cypraea. 



CEAJSTIA. Eetzius, 1788. {Cranium, a skull.) Fam. Eudistes, 

 Lam. Order, Pallio-brancliiata, Bl. — Descr. Inequivalve, equi- 

 lateral, irregular, sub-quadrate ; upper valve pateliiform, conical, 

 witli the umbo near the centre ; lower valve attached by its outer 

 surface ; muscular impressions, 4 in each valve ; two large, pos- 

 terior, distant ; two small, near to each other, central. No 

 hinge teeth ; no ligament, — 06s. This genus properly belongs to 

 the Brachiopoda, Lam. It differs from Orbicula in the mode of 

 attachment, which in the latter, is by a byssus passing through 

 the lower valve, and not by the valve itself. Hipponyx has only 

 two muscular impressions in each valve. The name of this 

 genus is derived from the inner surface of the attached valve, 

 which presents a remartabie resemblance to the facial portion of 

 a human skull. This appearance is caused by the situation and 

 elevated edges of the muscular impressions. Coasts of Britain 

 and Mediterranean. The monograph in Thesaurus contains 

 four species, PL xi. fig. 197. 



CEASSATELLA. Lamarck, 1801. (Crassus, thick.) Fam. Mac- 

 tracea. Lam. Conchacea, Bl. — Descr. Equivalve, inequilateral, 

 close, thick, rounded anteriorly, rostrated posteriorly, with den- 

 ticulated margins, smooth, or ribbed transversely ; hinge with a 

 triangular pit containing the cartilage, two anterior cardinal 

 teeth, and a posterior depression in one valve ; one anterior 

 tooth and a slight anterior marginal elevation, and a posterior 

 elevation in the other valve. Muscular impressions distant, 

 strongly marked. Palleal impression not sinuated. — Obs. The 

 few recent species known are marine, several being brought 

 from the coasts of New Holland. Fossil species are found in 

 Calcaire-grossier and London clay. The Crassatella are known 

 from the Veneres, &c., by the ligamentary pit in the hinge, and 

 from Lutraria and Mactra by the thickness and closeness of the 

 shell. C. rostrata. PI. iv. fig. 84. 



CEASSINA. Lamarck, 1818. Astarte. J. Sowerby, 1816. 



CEASSIPEDES. Lam. {Crassiis, thick ; pes, foot.) The first 



K 



