272 Mr. Barnes on the Genera Unio and Alasmodonta. 



CIA TT r> TT" i£? ^ outline of 



24.UN.oPLANUS.Flg. 16.^ „^^^^^„ 



Shell rhombick-oval, thin, beaks depressed ; disks 

 flattened, compressed; teeth slightly elevated, 

 smooth. 



Inhabits the Wisconsan. Mr. Schoolcraft. 



My Collection. 



Diam. 1"3 Length 2-8 Breadth 4-8. 



Shell with the beaks flat, ligament broad and deeply in- 

 serted between the valves ; hinge margin straight and par- 

 allel to the base ; basal margin slightly arcuated ; anterior 

 dorsal margin subtruncate ; epidermis brownish yellow ; 

 surface deeply wrinkled ; cardinal teeth smooth, polished 

 and slightly elevated ; lateral teeth long and slender ; ci- 

 catrices rough ; cavity very small ; naker bluish white tin- 

 ged With purple and green. Internal surface wavy and tu- 

 berculated. 



Remarks. — The flatness of the shell and the smooth- 

 ness of the teeth, readily distinguish this species from all 

 its congeners hitherto described. It has been supposed to 

 be the Unio Anodontina of M. Lamarck ; but besides being 

 four times as large, it has not at all the general habit of an 

 Anodonta ; v^herereas M. Lamarck observes that his shell 

 " might be mistaken for an anodonta unless it should be 

 carefully observed." 



***** Cardinal teeth small, oblique. 

 25. Unio Triangularis. Fig. 17. \ ^^^"u4ide. 

 Shell triangular, gibbous inflated, rayed, gaping ; 

 anterior slope flattened, ribbed, cancellate ; in- 

 side white. 



Inhabits Bois-blanc Isle, Detroit River. Major Delafield. 

 Dr. Mitchill's Cabinet. 

 Major Delafield's Collection. 

 My Collection. 



