﻿CLAMS, MUSSELS, AND OYSTERS. 



47 



By referring to the accompanying figures, these parts 

 may be readily made out : 



Fig. 46. — Oyster attached by Left Valve to a Stone. 



Fig. 47. — Oyster with the Left Valve removed. — h, Heart; I, Ligament; m, Position 



of Mouth. 



46. The pupil will now recall some characters in common 

 between the snails, and the mnssels, 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 



