260 Mr. Barnes on the Genera Unio and Alasmodonta. 



Diam. .7—1.3 Length 1.2—2.3 Breadth 2.1—3,7 inches. 



Shell transversely elongated, sub-pentangular, moderately 

 thick, rounded behind ; heaks slightly elevated, approxi- 

 mate; hinge margin straight, elevated, compressed, keel- 

 shaped, longitudinally furrowed, fuscous with submembra- 

 naceous strise; anterior dorsal margin straight and sub- 

 truncate; basal margin rounded; epidermis ^VQ^msh. yellow, 

 with brofld d^rk green rays; surface glabrous. Cardinal 

 teeth sliglitly striated, nearly smooth; posterior cicatrix 

 deep and striated ; naker very white, iridescent. 



Variety (o) obscurely rayed, more convex, compressed on 

 the base, and gaping behind. 



Inhabits Lake Champlain. 



My Collection. 



Remarks. — This is a beautiful species. It cannot be 

 confounded with any of the varieties of the Cariosus or Ra- 

 diatus, on account of the primary teeth, which are entirely 

 different. We have so many specimens of this shell, and they 

 are all so perfectly characterized, and so much alike, that 

 there can he no doubt of its being entitled to a distinct appel- 

 lation. In several of the specimens, the epidermis is worn 

 off, exhibiting a flesh-coloured substance beneath. 



12. UNIO ALATUs. — Shell ovately triangular; hinge 

 margin elevated into a large wing ; valves grow- 

 ing together on the back of the ligament, inside 

 purple. 



Unio Alatus. Mr. Say.. 

 Unio Alata. M. Lamarck. 

 American Conchology, plate 4. fig. 2. 

 Inhabits Fox River. Mr. Schoolcraft. 

 Wisconsan. Capt. Douglass. 

 Cabinets of the Lyceum and Dr. Mitchill. 

 We have every size of this shell from one inch to six 

 inches and nine tenths broad. A full grown specimen 

 measures as follows, viz. 



Diam. 2.0 Length 4.7 Breadth 6.9 



A middle aged and very splendid specimen measures 

 D 1.6 L 4.0 B 6.0 



