126 Mr. Barnes on t?ie Genera Unio and Masmodonta. 



projecting on the anterior basal edge; irregular profound, 

 nodulous undulations radiating from the elevated ridge to 

 the hinge and anterior margin. Cardinal teeth crenated ; 

 lateral teeth long and striated ; posterior muscular impres 

 sion deep, and the anterior half of it rough. Cavity^ angu- 

 lar compressed, directed backward under the cardinal tooth, 

 admitting the end of the finger. Maker pearly white, with 

 irregular spots of greenish, iridescent on the fore part. 



9. Unio Rugosus. Fig. 9. 



Shell broad ovate; surface wrinkled tuberculated, ribbed, 

 waved; disks swelled ; base falcated. 



Hab. Ohio. Mr. Collins. 



Mr. Collinses Collection. 



Length, 2-3 Breadth, 2-9 Diam. V5 



Shell narrowed, compressed and thin before ; short, ob- 

 tuse, rounded and wider behind; beaks slightly elevated; 

 ligament more elevated than the beaks ; hinge-margin 

 compressed, carinate ; basal margin falcate, emarginate, 

 and compressed ; anterior margin sub-angulate ; anterior 

 dorsal margin sub-truncate, nearly straight; anterior, basal 

 margin projecting. Epidermis dark brown, under the epi- 

 dermis pearly white. Surface rough and scaly, wrinkled 

 transversely and waved longitudinally, having distant irreg- 

 ular transversely compressed tubercles ; a broad nodulous 

 elevated somewhat double ridge extending from the beaks 

 to the anterior basal edge, and projecting on that part ; a 

 broad furrow or wave behind the ridge ending in the emar- 

 ginate basal edge ; and a furrow before separating the ante- 

 rior lunule ; small oblique waves radiating from the ridge to 

 the hinge and anterior dorsal margin. Cardinal teeth sulca- 

 ted; lateral tooth striated rough and in the left valve some- 

 what double : Posterior muscular impression deep and 

 partly rough. Cavity of the beaks angular, compressed and 

 directed backward under the cardinal tooth. Maker pearly 

 white, and on the fore part iridescent. 



Remarks. — This shell agrees in some parts of its descrip- 

 •tion with the U. Tuberculatus. It is, however, while of the 

 same length, of only a little more than half the breadth, and 

 yet of longer diameter. The tubercles, also are very dif- 

 ferent. In the U. Tuberculatus they are compressed Ion- 



