l6 DESCRIPTIONS OF 



Shell smooth, oblique, inflated, angular behind and rounded before, very inequi- 

 lateral ; substance of the shell rather thick, thinner behind ; beaks prominent, minutely 

 folded ; ligament rather long and somewhat thick ; epidermis dark olive, striate, with 

 three green rays on the posterior slope ; umbonial slope subangular ; cardinal teeth 

 long and lamellar, double in the right and single in the left valve ; lateral teeth very 

 long and somewhat curved; anterior cicatrices distinct; posterior cicatrices confluent ; 

 dorsal cicatrices placed on the posterior inferior portion of the cardinal tooth ; cavity 

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

 nacre white and iridescent. 



RemarTcs. — One specimen and a single valve were all which came with the shells 

 from Dr. House. In outline and general appearance it approaches U. Tigris, Fer., 

 from Bagdad. But it is a larger species, not of so fine a polish, and the cardinal teeth 

 are longer and more lamellar. In outline it also has some affinity to TL ni.siic.us, 

 herein described, but it differs in being more oblique and being without tubercles. 



Unio humilis. pi. 26, fig. 10. 



Testa plicata, transversa, subinflata, subaequilaterali, subcylindracea, postice biangulata; valvulis tenuibus, 

 pellucidis ; natibus prominulis, perplicatis ; epidermidc virido-.lutea, striata ; dentibus cardinalibus 

 lamellatis rectisque ; lateralibus longis lamellatisque ; margarita caeruleo-alba et iridisoente. 



Shell plicate, transverse, somewhat inflated, subcylindrical, nearly equilateral, bi- 

 angular behind ; valves thin, transparent ; beaks somewhat prominent and much 

 plicate; epidermis greenish yellow, striate ; cardinal teeth lamellar and straight ; 

 lateral teeth long and lamellar ; nacre bluish white and iridescent. 

 Proc. Acad. Nat. Sci. Vol. 8, p. 93. 



Hah.—Siam. S. R. House, M. D. 



My cabinet and cabinet of W. A. Haines, New York. 

 Diam. -4, Length -5, Breadth 1 inch. 



Shell folded, wide, somewhat inflated, subcylindrical, nearly equilateral, biangular 

 behind; substance of the shell thin, transparent; beaks somewhat prominent, sub- 

 medial, much folded at the tips ; ligament rather short and thin ; epidermis greenish 

 yellow, the green predominating on the folds, striate ; umbonial slope subangular ; 

 cardinal teeth lamellar and straight, double in the rigid and single in the left valve ; 

 lateral teeth long, lamellar, straight, double in the left and single in the right valve ; 

 anterior cicatrices confluent ; posterior cicatrices confluent, scarcely perceptible ; dorsal 

 cicatrices invisible ; cavity of the shell rather deep ; cavity of the beaks shallow and 

 subangular; nacre bluish white and very iridescent. 



Remarhs. — There are eight specimens of this small species of various ages before 

 me, the largest of which is not an inch wide. In its general phase it resembles U. 

 crispahis, Gould, but differs in being a smaller species, much thinner and having fewer 



