39 



very thick, oval, inequilateral, gaping at both ends, 

 coarsely wrinkled transversely ; beaks subcentral, from 

 which two longitudinal ridges cross the shell like the 

 letter V. ; posteriorly a little rounded, anteriorly ob- 

 liquely rounded, the edge incurved: a single conic 

 tooth and two muscular impressions in each valve. 2... 

 3,5. Scarborough) rare. Much shorter in breadth 

 than the My a Glycimeris of'Linneus, having rather the 

 outline of My a Truncata. 



TRIBE. MYARIA. 



Having a broad spoon-like tooth in each valve or in 

 one only : gaping at one or both extremities. 



GENUS. MY A. 



Transverse) gaping at both extremities) with one large 

 dilated projecting and nearly vertical cardinal tooth 

 in the left valve and with a hollow in the opposite 

 valve ; ligament internal, short, thick, and inserted 

 in the hollow of the primary tooth on the one side, 

 and in the pit of the other valve. 



* The real PANOPEA GLYCIMERIS. (Mya. G. of Lin. 

 Don. t. 142. P. ALDROVANDI, Lam. is still too 

 doubtful a native to be at present inserted in our 

 Catalogue. 



