282 Dr. Hildreth on fresh water Shells, 



projecting; anterior basal, arcuated; basal and posterior 

 margins, rounded ; epidermis, greenish brown ; corrugated 

 and tuberculated over the center and anterior parts of the 

 shell ; tubercles large near the center of the disks, and very 

 fine and beautiful on the beaks ; wrinkled across the trans- 

 verse striee on the anterior lunule, giving it a feather shaped 

 appearance ; a broad, elevated, and nodulous ridge extend- 

 ing from the beaks to the anterior margin, and projecting 

 in front ; cardinal teeth sulcated and deeply crenated ; late- 

 ral teeth, short, thick, rough and terminating abruptly, mus- 

 cular impressions nearly smooth, and the sulcus in the cardi- 

 nal tooth as deep as the bed of the posterior cicatrix ; cavity, 

 deep and angular; naker, a rich pearl color, tinged with 

 blue, and iridescent on the fore part ; a very beautiful shell 

 in its exterior, and not less admirable on the inside. 



No. 11. Unio Tuberculatus. — Fig. 11. 



Shell, long ovate ; surface, corrugated, waved tubercula- 

 ted, ribbed, disks compressed ; base arcuated. 



Length, 3.00 ; breadth, 5.00 ; diameter, 1.5. — Hab. Duck 

 Creek. 



Shell, thick and rugged ; anterior side compressed, nar- 

 rowed, thin; posterior side, rounded, short, obtuse and broad- 

 er than the anterior ; beaks flat, and far back ; ligament high- 

 er than the beaks ; hinge margin, nearly strait, elevated, 

 compressed ; anterior dorsal, emarginate ; anterior basal, 

 emarginate; anterior margin, rounded; epidermis, dark 

 brown ; surface, thinly and irregularly tubereulated ; tuber- 

 cles, elongated longitudinally ; an elevated ridge extending 

 from the beaks and projecting on the anterior basal edge ; 

 irregular nodulous undulations, radiating from the elevated 

 ridge to the hinge and anterior margins ; cardinal teeth, cre- 

 nated ; lateral teeth, long and beautifully formed ; posterior 

 cicatrix, deep, and anterior half rough ; cavity, angular, 

 compressed and directed backwards ; naker, pearly white, 

 with spots of greenish, and most splendidly iridescent with 

 purple, violet and gold, on the fore part. 



No. 12. Unio Rugosus. — Fig. 12. 



Shell, broad ovate ; surface, tuberculated, ribbed, waved, 

 disks swelled, base falcated. 



Length, 1.6 ; breadth, 1.8 ; diameter, 1.2. ; specimen 

 small. — Hab. Muskingum. 



