BIVALVES — MYA. 11 



II. 



l$il)al^^0. 



MYA. — Truncate Trough-shell or Gaper. 



4.nimal — anAscidia: Shell Bivalve^ generally gaping at 

 one end; hinge with hroady thicks strong teeth, seldom 

 more than one, and not inserted into the opposite valve, 



THIS genus may properly be called the first on the list 

 of Bivalves; its species, however, are by no means nu- 

 merous, their number being limited to twenty-six. 



The principal characteristic of the Mya consists in its 

 gaping at one end: the next general distinguishing mark 

 is— its having a single, broad, patulous tooth, proceeding 

 from beneath the beak. This tooth differs from that of 

 the foregoing genus, in as much as it is otherwise shap- 

 ed ; for, in the Pholas, it is long and slender, and almof.t 

 of equal size throughout ; whereas, in the Mya, it is much 

 wider and broader at one end than the other; and the 

 broadest end has an' excavation, which gives it the ap- 

 pearance of the bowl of a spoon or ladle. 



However, this sort of tooth is not always discernible m 

 pyery species of the Mya, for some are entirely without 



