65 



anterior twisted, extended; length f diam. ^ 

 axis T 5 of the breadth ; nacre bluish ; breadth 

 one third, or half an inch ; epidermis variable, 

 black, blackish, brown, brownish, olive ; reddish 

 brown, horn colour, &c.; apices rounded, not pro- 

 minent. Found in the Ohio, and adjacent rivers ; 

 no intermediary teeth. 



SPECIES LXIII. Cyclas aqualis (Phymesoda 

 cequalis.) 



Shell translucent, ventricose, rounded; wrinkles 

 close together, almost equal, obtuse ; lamellar 

 teeth somewhat flexuous, short, distant, equal ; 

 intermediary tooth oblique, single in each valve ; 

 epidermis corneous ; nacre bluish. Length 

 diam. f of the breadth ; axis medial. 



A small species ; length one quarter of an inch, 

 rare ; found in the Ohio ; internal tooth scarcely 

 apparent, obliquely inclined posteriorly ; right 

 valve with two oblong lamellar and almost equal 

 fossules ; the left valve with a corresponding la- 

 mellar tooth ; apices rounded, not prominent. 



