42 



differ, having teeth at the hinge, and from the latter 

 by the ligament being placed on the shortest side of 

 the shell, which is transverse, widely gaping on either 

 side; hinge callous without teeth, with externally pro- 

 jecting callosities. 



Glycimeris margaritacea. 





MYA. 



MYA TRUNCATA, LlUtlCBUS. 



Chem.6,tA,f. 12. 

 These shells are marine bivalves, transverse, inequila- 

 teral, not always equivalve, gaping at the two extremi- 

 ties, one of which is often obtusely truncated. Hinge 

 with a very singular large compressed spoon-shaped 

 tooth, rising perpendicularly from the plane of the left 

 valve, and fitting into the entrance of the primary ca- 

 vity corresponding with it on the opposite valve, when 

 both are closed; ligament interior, short, thick, and at- 

 tached to the projecting tooth on one side, and to the 

 cavity on the other. These shells remain concealed 

 in the sand, through which they protrude a long mem- 

 branous tube, enveloping two smaller ones. 

 \i\i truncate Mya erodona 



• • • arenaria — solenimyalis. 



