Mr. Barnes on the Genera Unio and Jllasmodonia. 123 



Mr. Collins's colleetion contains a specimen from the 

 Ohio of the following dimensions. 



Diam. 1-0 Length, 1-5 Breadth, 18 



Shell thick, roimded behind, sub-biangulate before. Beaks 

 somewhat elevated and nearly central, with the ligament 

 passing between them; anterior lunule long-heart-shaped, 

 compressed, distinct by a roundish elevated ridge which 

 ends in a projection on the anterior margin, and marked by 

 small transverse, sub-nodulous wrinkles, and obsolete longi- 

 tudinal furrows; surface waved and on the fore part com- 

 pressed; a regular row of large, distant, elevated and trans- 

 versely compressed tubercles, extends from the beaks to the 

 basal edge, dividing the shell into two nearly equal parts. Car- 

 dinal teeth, sulcated. Maker, pearly white, and iridescent. 



Remarks. — This shell resembles the last in its color, out- 

 line, and glabrous surface. The teeth very much resemble 

 those of the last, and there is also in the left valve, the rudi- 

 diment of a second internal lateral tooth. The principal dif- 

 ference is in the smaller size of the present shell, and the re- 

 markable row of horns, which furnish the specific designa- 

 tion. These horns are not opposite to each other, but al- 

 ternate, and the highest one is in the right valve, nearly as 

 high as the summit. In both the above mentioned speci- 

 mens, the number of horns is three on each valve, and the 

 rudiment of a fourth on the extremity of the basal edge. 

 We rarely find shells from different and distant localities so 

 much alike. Almost the only difference is in the elevation 

 of the beaks of the former being greater than that of the lat- 

 ter. Exclusive of the beaks, the length, breadth and diam- 

 eter of the shells, is precisely the same. 



6. Unio Verrucosus. Fie. 6. < ,* , .,' 

 ° (6. outside. 



Shell sub-longitudinal, sub-truncate before, irregularly tu- 



berculated ; tubercles transversely compressed ; inside 



brownish red. 



Hab. Ouisconsin River. Mr. Schoolcraft. 



Lake Erie. Major Delafield. 



The collections before mentioned. 



Diam. -G—l-e Length, l-7~3-05 Breadth, 1-95— 3-15 



Shell sub-quadrangular, thick, rounded behind, biangu- 



late and sub-truncate before ; beaks elevated and recurved 



