NEW UNIONIDvE OF THE UNITED STATES. 91 



also more quadrate, and the lines of growth are more distinct. It reminds one of 

 nitens (nobis), and has a nacre of purple in the cavity, and salmon color in the lower 

 part of the valves. It is, however, more quadrate, and the beaks are more medial. 

 The tips of the beaks are imperfect in this specimen, but there is an appearance of a 

 few rather coarse undulations. It is also allied to liebes (nobis), but that is a much 

 larger species, more transverse, and more compressed. 



Unio irrasus. PL 13, fig. 239. 



Testa lsevi, rotundo-trigona, inflata, postice obtuse angulata, antice rotunda; valvulis subcrassis, autice 

 crassioribus ; natibus subelevatis, crassis ; epideroiide luteo-fusca, vel obsolete radiata vel eradiata ; 

 dentibus cardinalibus crassis, elevatis, subeouipressis erenulatisque ; lateralibus curtis, crassis, obliquis 

 rectisquc ; margarita argentea et iridescente. 



Shell smooth, rotundo-triangular, inflated, obtusely angular behind and round 

 before ; valves rather thick, thicker before ; beaks rather raised and thick ; epidermis 

 yellowish brown, obscurely rayed or without rays; cardinal teeth thick, elevated, 

 somewhat compressed and crenulate ; lateral teeth short, thick, oblique and straight ; 

 nacre silver white and iridescent. 



Proc. Acad. Nat. Sci. 1861, p. 38. 



Hob. — Etowah River, Georgia. Rev. G. White. 



My cabinet and cabinet of Mr. White. 

 Diam. -7, Length IT, Breadth 1-4 inch. 



Shell smooth, rotundo-triangular, inflated, obtusely angular behind, round before ; 

 substance of the shell rather thick, thicker before ; beaks rather raised and thick ; 

 ligament thick, short and light brown ; epidermis yellowish brown, without rays or 

 obscurely rayed, with numerous close lines of growth ; umbonial slope slightly raised 

 and rounded ; posterior slope rather broad, rather depressed, with two raised lines on 

 each valve from the beaks to the margin ; cardinal teeth thick, elevated, compressed, 

 and crenulate ; lateral teeth short, thick, oblique and straight ; anterior cicatrices dis- 

 tinct, small, and deeply impressed ; posterior cicatrices distinct, rather small and 

 well impressed ; dorsal cicatrices placed on the plate within the cavity of the beaks ; 

 cavity of the shell rather deep and rounded ; cavity of the beaks rather shallow and 

 obtusely angular; nacre silver white and iridescent. 



Remarks. — This is a small species which while it reminds one of trigonus (nobis), is 

 more rotund, approaching to ebenus (nobis), but it cannot be confounded with either. 

 It is smaller than either, and not by any means so thick and solid, the largest being 

 only 14 inch by 1|. It is also more lenticular. The lines of growth are close and 

 well marked, there being twelve on the oldest of nearly a dozen specimens in my 

 possession. One of the specimens has close, dark green rays over the umbones and 

 towards the tips of the beaks. No soft parts were xx-ceived with these. 



