﻿CLAMS, MUSSELS, AND OYSTERS. 



47 



By referring to the accompanying figures, these parts 

 may be readily made out : 



Fig. 4G. — Oyster attached by Left Valve to a Stonh. 



Fig. 4T. — Oystee wixn tiie Left Valve removed.—^, Heart; /, Ligament; ?«, Position 



of Mouth. 



46. The pupil will now recall some characters in common 

 between the snails, and the mussels, clams, and oysters, thus 

 far studied in these lessons, namely : they all have the body 

 protected by a limy shell (except the slug), this shell either 

 composed of one piece, as in the snails, or of two pieces or 



