146. AMERICAN JOURNAL 



4. Unio opalinus, Anthony. — t. 7, f. 2. 



Description. — Subrhomboidal, somewhat inflated, rather 

 thick; lines of growth becoming varicose anteriorly; beaks 

 placed near to, and pointed towards, the anterior end of the 

 shell, with several doubly-curved undulations ; ligament mar- 

 gin straight and slightly declining, posterior slope and margin 

 sub-biangular, basal margin almost straight, anterior margin 

 somewhat rounded; epidermis light yellowish or greenish, 

 iridescent. Cardinal teeth small, lateral teeth long and straight ; 

 cavity of the shell moderate, of the beaks rather deep and 

 angular ; anterior cicatrices distinct, posterior cicatrices con- 

 fluent and indistinct, dorsal cicatrices in the cavity of the 

 beaks ; nacre pearly, very iridescent posteriorly. 



Dimensions. — Length If inches, breadth 1 inch, diameter J 

 inch. 



Locality. — Michigan, 



Collection Mus. Comp. Zoology, Cambridge, Mass. 



Observations. — Eesembles somewhat Unio Sayi, but is longer 

 in proportion to the breadth ; the beaks are placed nearer to 

 the anterior end, and the species is much smaller. It may 

 also be compared with Unio gibbosus, Barnes, which it cer- 

 tainly resembles in general form. It is, however, more bi- 

 angular behind ; the color is very different, being dark and 

 rayed in gibbosus; the latter is also a heavier species, the nacre 

 either salmon, purple, or white, very much thickened ante- 

 riorly, and the cavity of the beaks very shallow. The undu- 

 lations of the beaks are more decidedly marked and closer in 

 opalinus than in gibbosus. 



5. GoNiOBASis ciNGENDA, Anthony. — t. 7, f. 3. 



Description. — Shell conic, smooth, olivaceous; spire elevated, 

 but decollate, exhibiting but 5 whorls, having lost at least 3 

 which it should have had in a perfect condition ; whorls con- 

 vex, slightly ridged below the middle, immediately below 

 ■which a broad, dark brown band passes around the upper 

 whorls, becoming double but confluent on the penultimate, but 

 distinctly double and distant on the body whorl ; sutures deep 

 and sharply defined ; aperture ovate and bluish within ; colu- 

 mella deeply rounded, curved at the base, forming with the 

 outer lip a distinct but not deep sinus; lines of growth very 

 distinct and curved. 



Dimensions. — Length 1 2-lOths inches, diameter | inch, 

 length of aperture | inch, breadth 4-lOths inch. 



Habitat. — North Carolina. 



