j^4 DESCRIPTIONS OF 



specimens of this species. It is not remarkable for any peculiar characters. In outline 

 it closely approaches H. ccerulem, (nobis,) but it differs in not having a bluish epider- 

 mis, in being more transverse, and in not possessing the fine undulations of the beaks 

 and the posterior slope. Neither of the specimens are entirely perfect at the tips of 

 the beaks, but I cannot perceive any indication of undulations. 



Unio rusticus. pi. 25, fig. 7. 



Testa tuberculata, elliptica, inflata, inajquilaterali, postic6 subangulata; valvulis subcrassis ; natibus sub- 



prominentibus; epidermide olivacea, substriata; dentibus cardinalibus longis lamellatisque ; lateralibus 



longis, lamellatis subrectisque ; margarita alba et iridescente. 



Shell tuberculate, elHptical, inflated, ingequilateral, subangular behind; valves 



rather thick ; beaks somewhat prominent : epidermis olive color, somewhat striate : 



cardinal teeth long and lamellar ; lateral teeth long, lamellar and nearly straight ; 



nacre white and iridescent. 



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



fia&.— Siam. S. R. House, M. D. 



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

 Diam. 1-1, Length 1-4, Breadth 2-3 inches. 



Shell tuberculate, elliptical, inflated, inequilateral, subangular behind and rounded 

 before ; substance of the shell rather thick ; beaks somewhat prominent, granulate ; 

 ligament rather short and somewhat thick ; epidermis olive colored, with three green 

 rays on the posterior slope ; umbonial slope subangular ; cardinal teeth long and lamel- 

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

 nearly straight; anterior cicatrices distinct; posterior cicatrices confluent; dorsal 

 cicatrices placed under the cardinal tooth ; cavity of the shell large and rounded ; 

 cavity of the beaks deep and subangular ; nacre white and iridescent. 



Remarhs. — There were about a dozen of this species submitted to my examination 

 by Mr. Haines, difiering very much from each other. Some of them are tuberculate 

 nearly over the whole surface, while others are almost entirely without tubercles. In 

 this it agrees with U. corrugatus, Retz, and U. Tavoyemis, Gould. In outline it closely 

 approaches U. Javanus, (nobis,) but is a rougher shell and the folds on the posterior 

 slope are coarser. In some specimens the tubercles about the beaks resemble those 

 of U. Murchisonianus, (nobis.) 



Unio eximius. PI. 25, fig. 8. 



Testa alata, plieata, obovata, compressa, vald6 inaequilaterali, postice rotundata; valvulis tenuissimis; nati- 

 bus prominulis ; epidermide virido-lutea, obsolete radiata ; dentibus cardinalibus lamellatis tenuibusque ; 

 lateralibus longis, lamellatis subcurvisque ; margarita c»ruleo-alba et iridescente. 



Shell winged, plicate, obovate, compressed, very inequilateral, rounded behind ; 



