1 24 Mr. Barnes on the Genera Jjnia and Alasmodonta. 



ligament deeply inserted between the valves; hinge-margin 

 nearly straight, compressed alated, heel-shaped, and making 

 an obtuse angle with the anterior margin; basal margin 

 rounded ; epidermis light green, tinged with reddish brown ; 

 surface of the anterior part studded with irregular transverse- 

 ly compressed tubercles. Cardinal teeth crenated or sul- 

 cated; cavity of the beaks very deep, compressed angular 

 and directed backwards under the cardinal tooth ; Naker 

 brownish red with a tinge of blue, or light chocolate color- 

 ed, slightly iridescent on the anterior part; the other dull 

 and not highly polished; posterior muscular impression 

 deep and rough. 



Variety [a.) has the epidermis of an uncommonly light 

 green without the brown tinge. 



Hab. Lake Erie. Major Delajield''s collection. 

 Diam. -8 Length, 1-65 Breadth, 1-9 



Variety (6.) is a slender and rather thin shell; epidermis 

 very pale green ; Naker pearly white, polished and irides- 

 cent. 



Diam. -9 Length, 1-6 Breadth, 1-9 



Locality and authority as before. 



*. Remark. — If a straight hne is drawn from the beak to the 

 base, through the cardinal tooth, it will divide the tubercu- 

 lated from the smooth part of the shell, in all except the va- 

 riety (6.) in which the tubercles extend a little farther 

 back. 



„ TT ■ \r 1 -r- K7 V ^- inside. 



7. Unio Nodosus. 1 ig. 7. • , . ., 

 ° (6. outside. 



Shell, sub-quadrangular, sub-longitudinal, emarginate be- 

 fore, knotted, ridged, corrugated ; lateral tooth terminating 

 abruptly, 



Hab. Ouisconsin. Mr. Schoolcraft. 



Collections o{ Lyceum and Dr. Mitchill. 



My Collection. 



Diam. 1 -8 Length, 2*5 Breadth, 3-0 

 Shell, thick and ponderous, short and very obtusely 

 rounded behind ; beaks distant, elevated, eroded, chalky or 

 greenish white, with the ligament passing between them. 

 Anterior lunule, compressed, wedge-shaped, separated by a 

 deep groove, ending in the emargination in front. Hinge-mar- 



