FAMILY 4. MYARIA 57 



MYOCHAMA, Stutchbury. 



Testa inaequivalvis, irregularis, adherens, dentibus duobus cardinalibus 

 divaricatis in utraque valva, fovea trigona intermedia cum appendice 

 testacea minima, cartilagine connexa, inserta. Valva affixa plana, 

 altera libera, convexa, costis vel sulcis interruptis, ab umbonibus ad 

 marginem radiatis, tecta. Ligamentum tenue, externum. Impres- 

 sio muscularis pallii sinu brevi, lato. 



This remarkable genus, of which but few specimens have been seen, 

 was introduced by Sowerby, and described by him as partaking of the 

 characters of the Myaria and Chamacea. Its shell, like that of Anatina, 

 is furnished with a testaceous appendage, and, as in that of Chama, the 

 lower valve is immediately fixed to some marine body. 



It may be described as inequivalve and irregular, with two diverging 

 cardinal teeth in each valve, in the centre of which there is a triangular 

 cavity, having a small testaceous appendage connected with it by a horny 

 cartilage. One valve is attached and flat, the other is free and very con- 

 vex, covered with ribs or interrupted grooves, radiating from the um- 

 bones to the margin. The ligament is thin and external. The palleal 

 impression exhibits a short broad sinus. 



Example. 

 PI. XXXIX. Fig. 1 to 4. 

 Myochama anomioides, Sowerby, Genera of Shells, No. 32. 



VOL. I. 



