MOLLUSC A. 41 



If Mya arenaria cannot be obtained, there are other 

 kinds of clams, which do not differ very much in their 

 more important characteristics. 



The triangular-shaped Hen Clam, or Beach Clam, 

 or Hard Shell, Mactra solidissima, is often found in our 

 markets also, and has shorter funnels and a light brown 

 shell, and a larger foot, and, on account of its size, is 

 a very favorable object for dissection (Fig. 24). The 

 tumid, blackish-brown shell of the Cyprina Islandica 

 distinguishes it at once from Mactra ; and, although 

 they are often represented as edible clams, they are not 

 considered good eating, and are rarely abundant 

 enough (Fig. 23). 



The Quahog, Venus mercenaria, is rare on the coast 

 of New England ; and south of Cape Cod it is very 

 abundant, and replaces the Mya arenaria in the mar- 

 kets (Fig. 22) . The funnels of this are also very short ; 

 and in place of being united, the tubes are partly sep- 

 arated. The interior of this shell is colored violet in 

 part, and formerly served the Indians, when cut into 

 flat beads, for ornament, and also as a medium of 

 exchange or money or ornament, being, in common 

 with the beads of a similar description, cut from the 

 conch shell and other suitable species, called wampum 

 by existing Indians. 



The Fresh-water Clam, Unio or Anodon, is a form 

 allied to the clam, and readily accessible to those who 

 live near large ponds or rivers in the interior. The 

 mantle in these is open all around, as in the oyster, but 

 the internal parts and the shell resemble those of the 

 clam. They have a foot, which, however, is used, not 

 for burrowing, but for crawling or rooting to a certain 



