CREPIDULA, 31 
large, posterior, distant; two small, approximate, central. No 
hinge teeth; no ligament. Obs. 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. Some specimens of 
this genus present in the muscular impressions, a curious resem- 
blance to the facial portion of a human skull. Some species 
occur in the Mediterranean, and some in the British seas. Several 
fossil species are described. C. personata, fig. 197. 
CRASSA’TED. (Crassus, thick.) Used to express a thickness 
in the substance of the shell. Hx. Glycimeris, fig. 67. 
CRASSATEL'LA. (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 marginalelevation, 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 Hol- 
land. Fossil species are found in Calcaire-grossiér and London 
clay. The Crassatellee 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. Astar’trE, Sow. 
CRAS'SIPEDES. Lam. (Cyassus, thick; pes, foot.) The first 
section of the order Conchifera Dimyaria, Lam. In this sec- 
tion, the foot of the animal is thick and the shell gapes con- 
siderably ; is divided into the families Tubicolz, Pholadidz 
Solenidz, and Myaria. Fig. 44 to 76. 
CRENA‘TED. (Crena, notch.) Applied to small notches, not 
sufficiently raised or defined, to be compared to teeth. As the 
hinge of Iridina, fig. 150. 
*CRENA’TUTA. Lam. Fam. Malleacea, Lam. Margaritacea, 
Bl. Descr. Compressed, lamellated, irregular, subequivalve, 
inequilateral, oblique; umbones terminal; hinge linear, nearly 
straight, with a series of excavations, containing the cartilage. 
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. Crenatula also has no passage for the byssus, as in 
Perna. C. Mityloides. Fig. 168. 
CREPIDULA. Lam. (Crepidula, little slipper.) Fam. Calyp- 
tracea, Lam.and Bl. Descr. Oval, irregular, patelliform; apex 
lateral, incurved or subspiral; external surface convex, smooth 
$$ CRENA TULA, cee exreli 
