120 Mr. Barnes on the Genera Unio and Alasmodonta. 



Maj. Del^field's collection. 



Diam. 1-7 Length, 2-3 Breadth, 3-1 

 Remark. — This shell is thinner than specimens of the 

 same size usually are. 



2. Unio Undulatus. Fig. 2. < 7* , •,* 

 ° (6. outside. 



Shell rhombick ovate, with numerous waving folds radia- 

 ting from the beaks. 



Unio Peruviana ? M. Lamarck. 



Taken by Mr. Collins in the Ohio and preserved in his 

 collection. 



Diam. 1'9 Length, 34 Breadth, 4*6 



Shell thick, very short and obtusely rounded behind ; 

 beaks slightly elevated; hinge-margin sub-alated, compress- 

 ed, carinated, distinct with a furrow on each side ; anterior 

 dorsal margin sub-truncate ; Epidermis blackish brown ; 

 surface finely wrinkled transversely ; wrinkles becoming 

 lamellar on the anterior side ; oblique folds deeply indent- 

 ing the anterior margin ; waves largest and deepest below, 

 not extending to the anterior dorsal margin, fine, numerous, 

 curved upwards, and extending to the ligament above ; 

 longitvdinal furrows extending from the beaks to the an- 

 terior dorsal margin ; decussating the oblique waves ; the 

 lowest furrow deepest, the other somewhat obsolete ; disks 

 tuberculated below the beaks. Cardinal teeth sulcated ; 

 posterior cicatrix very rough and deep; Naker pearly white, 

 irregularly spotted with brownish green. 



Remark, — A large and very beautiful shell. 



3. Unio Plicatus. Fig. 3. < 7* , •,* 

 ° i 0. outside. 



Shell sub-quadrangular, tumid, sinuous before with dis- 

 tant oblique folds ; hinge-margin elevated, compressed, car- 

 inated. 



Unio plicata. Le Suenr. Mr. Say. 



Unio Rariplicata. M. Lamarck. 



Hab. Ohio, Mississippi, and Ouisconsin. 



