LIST OF PLATES. IX 



3. Cardium lavigatum, or Smootli Cockle. 

 3, 4. Isocardia cor. 



Plate XI. 

 1. Area tetragona. 

 3. L(Bda caudata; differing in shape from Nucula, but the hinge 



having two rows of sharp, angular teeth, and a central pit, 



as in that genus. 



3. Nucula nucleus ; interior of one valve. 



4. Peetuneulus pilosus ; having an arched hinge, with two rows 



of angular teeth, and the ligament placed on an external 

 area. 



5 . Young and striped specimen of Mytilus edulis, or the common 



eatable Mussel, showing the narrow, white foot, and the 

 byssal cords attaching the bivalve to the rock. 



6. Dreissina polymorpJm ; having a septum across the interior 



at the small end. 



Plate XII. 



1. Lima, showing the cilia and foot of the animal outside the 



valves. 

 3. Anomia epMppium. The small figure shows the bony button 



passing through an opening in the lower valve, by which 



the Anomia is fixed to the rock. 



3. Peeten niveus, or White Scallop; showing the ocelli, or eye- 



like spots, and cilia. 



4. Anodonta cygnea. 



5. Terebratula ca/put-serpentis ; attached to a rock by means of 



