MOLLUSCA. LAMELLIBRANCHIATA. 



127 



plough-share shaped, and is used for crawling, or for 

 burrowing in sand or mud. Sometimes as in the cases of 

 Trigonia and Cardium, by means of a rapid movement, it 



FIG. 44. Mya arenaria. The left valve and mantle, and also half the 

 siphons, have been removed, a, anterior adductor muscle; a', 

 posterior adductor; b, visceral mass; c, cloacal chamber into which 

 the anus opens ; /, foot ; g, branchiae ; h, heart ; m, cut edge of the 

 mantle ; o, mouth ; s, branchial siphon ; s', anal siphon ; t, labial 

 palps ; v, anus. (From Woodward.) 



