96 LABORATORY STUDIES IN ZOOLOdV 



Carefully separate the mantle lobes just caudad of the posterior 

 adductor muscle and trace the caudal course of the intestine 

 which lies exposed along the caudal border of the muscle. It 

 terminates in the anus, which opens into the cloacal or exhalant 

 siphon at a level with the ventral margin of the posterior adductor 

 muscle. 



Make an outline drawing, each valve four and a half inches 

 long, of the united halves of the shell with the left valve at the 

 top of the page. In the left valve represent the inner surface 

 of the shell and also show any external structures which may be 

 visible from this aspect. In the right valve show as many 

 details as possible of the soft parts discussed above. Indicate 

 the course of the respiratory current by means of arrows. 



