102 



epidermis yellow, polished, with numerous obsolete 

 rays; within white; cardinal teeth double in each 

 valve, oblique, prominent; lateral teeth lamellar, very 

 prominent. 



OBSERVATIONS. 



I found a few specimens of this species about two 

 years since in Salina lake, New York, and delayed 

 the publication of it in the expectation of obtaining 

 other specimens. The young and adult shells, how- 

 ever, are before me, and present a marked difference 

 to either cariosus or siliquoideus, the two kindred 

 species which abound in the neighbouring waters. 

 It is proportionally shorter and less inflated than the 

 latter, and differs more obviously in being destitute 

 of distinct rays. It is proportionally longer, less 

 inflated, and has a longer ligament margin than the 

 cariosus; the cardinal teeth are very different. 



UNIO SAY ANUS. 



Plate LV.— Fig. 2. 

 DESCRIPTION. 



Shell subrhomboidal, rather thin, slightly ventri- 

 cose; beaks prominent, obliquely plicated; anterior 

 margin obtusely rounded; ligament margin scarcely 

 declining, straight, angulated at tip; umbonial slope 

 rounded; posterior margin subrectilinear, oblique, ex- 

 tremity rather acutely angulated, the angle being 

 considerably above the line of the base; basal margin 



