﻿CLAMS, MUSSELS, AND OYSTERS. 



41 



^y^<t 



ex. zn. 



B A f 



Fig. 42.— Common Clam. — A. showing Siphons partly extended; in., Incurrent Orifice; ex., 



Excurrent Orifice ; f, Foot ; in, thickened border of the Mantle projecting beyond the 



Edge of the Shell ; B, Siphons, greatly extended. (The shell is not drawn, as there was 



no room for it on the page.) The excurrent and incurrent orifices are more open than in A. 



