12 



A. BIVALVES. 



1. Cyclas. 



2. Anodon. 



3. Unio. 



4. My sea. 



I. CYCLAS. 



Shell bivalve, equivalve, orbicular or oval, closed all 

 round. Hinge with two minute divergent primary 

 teeth in each valve ; and an elongated lateral one 

 on each side, which is doubled in one of the valves. 

 Licrament external. 



* Somewhat orbicular and equilateral. 



1. Cyclas rivicola. Shell rather convex and opake, 

 with regular close-set transverse striae. 



Cyclas rivicola. Turton, Dith. p. 248. t. 11. f. 13. 



Lamarck, y. p. 558. 

 Cyclas cornea. Draparn. p. 128. 1. 10./. 1 — 3. 

 Tellina cornea. Wood, pi. 46./. 3. 

 Cardium corneum. Montagu, p. 86. large var. 



