ORDER II. 



)!$ibali)e0* 



MYA. Trough-shell, or Gaper. 



DESCRIPTION OF PLATE IV. 



Fig, 1. M. Arenaria. Fig. 3. M. Corrugata. 



Fig. 2, M. Pubescens. Fig. 4. M. Aurita. 



Shell bivalve, generally gaping at one end. 



THIS genus is placed by Linnaeus the first on the 

 list of Bivalves; the number of its species amounts to 

 forty. 



The principal characteristic of the Mya consists in 

 its g-aping' at one end : the next general distinguishing 

 mark is, its having a single, broad, patulous tooth, pro- 

 ceeding from beneath the beak. It is much wider and 

 broader at one end than the other; and the broadest 

 end has an excavation, which gives it the appearance 

 of the bowl of a spoon. 



The form of the Mya varies exceedingly: some are 

 oblong and truncated ; others, again, are orbicular or 

 round ; and many are angular or eared. 



