262 Mr. Barnes on the Genera Unio and Alasmodonta. 



Unio purpurata? M. Lamarck. 

 Inhabits Fox River. Mr. Schoolcraft. 

 Wisconsan. Capt. Douglass. 

 ' Cabinets of the Lyceum and Dr. Mitchill. 

 My Collection. 

 Diam. 1.7—2.1 Length 2.5—2.7 Breadth 5.8—6.4 

 Shell very long oval; anterior side somewhat pointed, 

 posterior side short, rounded, obtuse ; beaks depressed ; lig- 

 ament elevated above the beaks ; basal margin slightly com- 

 pressed, shortened, or, in old specimens, arcuated; in young 

 rounded ; epidermis blackish brown, with fine interrupted 

 wrinkles placed in longitudinal rows, having somewhat the 

 appearance of striae. Young specimens are rayed with yel- 

 lowish olive, and have the epidermis smooth and glabrous. 

 Naker purple of different shades according to the age or per- 

 fection of the specimen, sometimes tinged with irregular 

 spots of greenish, particularly under the beaks, with a row 

 of small muscular impressions in the cavity. 



Remarks. — This shell is probably the Unio purpurata of 

 M. Lamarck. (See introductory remarks.) We have every 

 size from the breadth of one inch, to six inches and four 

 lines. 



Variety (a.) Shell on the inside striated longitudinally. 

 Naker red-purple, very splendid. 



Variety (b.) Naker whitish green on the margin, and pur- 

 ple in the centre. An uncommonly beautiful shell, tinged 

 with copper ? 



My Collection. 



, , T- 1 ci ^ «• inside. 



14. UNIO GIBBOSUS. Fig. 12. ^ ^ ^^^^j^^ 



Shell elongated transversely, thick, gibbous : lateral 

 tooth very thick, incurved, inside purple. 



Inhabits Wisconsan. Mr. Schoolcraft. 



My collection. Lyceum's Cabinet. 

 Mr. Say's Collection. Philadelphia. 

 Diam. .75—1.3 Length 1.15—1.9 Breadth 2.4—4.0 

 Shell much elongated transversely, thick and heavy, ra- 

 pidly narrowed and rostrate before, narrow and rounded be- 



