CRASSATELLA. Lam. (_Crassus_, thick.) _Fam._ Mactracea, Lam. Conchacea, Bl.--_Descr._ Equivalve, inequilateral, close, thick, rounded anteriorly, rostrated posteriorly, with denticulated 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. Fig. 84, C. rostrata. CRASSINA. Lam. ASTARTE, Sow. CRASSIPEDES. Lam. (_Crassus_, thick; _pes_, foot.) The first section of the order Conchifera Dimyaria, Lam. In this section the foot of the animal is thick, and the shell gapes considerably. It is divided into the families Tubicolæ, Pholadidæ, Solenidæ, and Myaria. Fig. 44 to 76. CRASSISPIRA. Sw. A genus separated from COLUMBELLA, Auct. for which Mr. Swainson quotes "Pleurotoma Bottæ, Auct." Crassispira fasciata, Sw. Lardn. Cyclop. Malac. p. 313. CRENATED. (_Crena_, a notch.) Applied to small notches, not sufficiently raised or defined, to be compared to teeth. _Ex._ The hinge of Iridina, fig. 150. CRENATULA. Lam. _Fam._ Malleacea, Lam. Margaritacea, Bl.--_Descr._ Compressed, foliated, irregular, sub-equivalve, inequilateral, oblique; umbones terminal; hinge linear, nearly straight, with a series of excavations, containing the cartilage, while the intervening ridges are covered with the ligament, properly so called. Muscular impression oblong, indistinct.--_Obs._ This genus is known from Perna by the hinge, which in the latter is composed of a series of regular, straight, ligamentary grooves placed across it. In Crenatula also there is no passage for the byssus, as in Perna. C. Mytiloides, fig. 168. Coasts of the Red Sea. CRENULATED. Finely crenated or notched.