162 



very numerous, obsolete greenish radii ; sometimes with more or 

 less obvious, transverse, yellowish bands' towards the base ; beaks 

 not elevated above the general surface, with two or three rows of 

 very small tubercles : hinge margin nearly rectilinear, compressed 

 behind, and anteriorly compressed almost into a wing : ligament, 

 particularly in the young specimen, concealed : posterior margin 

 rounded : anterior margin a little prominent, obtusely angulated ; 

 basal margin much arquated : within undulated almost as obvi- 

 ously as on the exterior ; pale bluish, varied with pale flesh color, 

 and somewhat iridescent before and behind : cicatrices slightly 

 impressed. 



Length about four inches. Breadth five and three-tenths. Con- 

 vexity nearly one inch and three quarters. 



A large and fine species. Some time since, Mr. 0. Evans 

 obtained an individual, which I hesitated to publish as new, think- 

 ing it might possibly be a young remote variety of the A. grandis, 

 nob., but subsequently, having received adult and perfect speci- 

 mens from Mr. Evans, I found that it is uniformly longer, more 

 rounded, much more compressed, and having a different aspect. 

 It is found in ponds, near the Wabash river, but rarely, if ever, in 

 the river itself, as it prefers still water and a muddy bottom. In 

 form it approaches nearer to orbicular, than any other species that 

 we have seen described. 



An American conchologist was of the opinion that all our Ano- 

 dontas are referrible to one species ; but we conceive that the 

 present species, cannot with more propriety be united with the 

 cataracta and marginata, nob., not to mention the more elongated 

 species, than the various species of Unio can be considered as no 

 other than U. picta, L. PI. 11. 



NucuLA. — Shell transverse, equivalved, inequilateral ; summits 

 contiguous ; hinge with a primary, more or less triangular fosset for 

 the reception of the ligament, with an anterior and posterior series 

 of small, inserted, numerous, pectinate teeth, interrupted at the 

 summit by the fosset ; ligament internal, very short, inserted into 

 the fosset ; muscular impressions two, simple. 



Ohs. A genus connected with Area, Pectuncidus, Cuculkea, 

 and Trigonia, but eminently distinguished by the ligament being 

 interior ; which, as has been remarked by Sowerby, proves their 

 relation to the Mactracese. Many species are known. Lamarck 



