12 DESCRIPTION OF FIFTY-TWO SPECIES OF UNIONID^. 



guished from cuneolus by its being more triangular, approaching the outline of 

 typical oUiquus, Lam. TuscumUensis is also closely allied to Edgarianus (nobis), 

 but differs in being less tumid, less polished, and less extended at the anteriar 

 basal margin. None of the specimens are perfect enough at the beaks to exhibit 

 undulation at the tips. 



Unio appressus. pi. 3, fig. 8. 



Testa Isevi, triangulari, securiformi, valde inEequilaterali, antice rotundata, postice subangulata ; vaU 

 vulis crassiusculis, antice aliquanto crassioribus ; natibus prominentibus ; epidermide flavida, 

 radiis interruptis postice indutis ; dentibus cardinalibus paviusculis, compressis crenulatisque ; 

 lateralibus sublongis, curvis lamellatisque ; margarita argentea et aliquanto iridescente. 



Shell smooth, triangular, securiform, very inequilateral, rounded before, sub- 

 angular behind ; valves somewhat thick, somewhat thicker before ; beaks promi- 

 nent; epidermis yellowish, covered behind with interrupted rays ; cardinal teeth 

 somewhat small, compressed, and crenulate ; lateral teeth rather long, curved, and 

 lamellar ; nacre silvery white and somewhat iridescent. 

 Proc. Acad. Nat. Sci., 1871, p. 189. 



Ha&.— Tuscumbia, Ala., B. Pybas ; Tennessee Eiver, J. G. Anthony ; Holston 



River, Miss Law and C. M. Wheatley. 



My cabinet ; cabinets of Mr. Anthony and Dr. Lewis. 

 Diam. -9, Length 1-5, Breadth 11 inch. 



Shell smooth, triangular, securiform, very inequilateral, rounded before and 

 obtusely angular behind; substance of the shell somewhat thick, thicker before; 

 beaks prominent; ligament rather short and dark brown; epidermis yellowish, 

 with interrupted rays on the posterior part near to the umbonial slope, with nume- 

 rous rather close lines of growth; umbonial slope obtusely angular; posterior slope 

 narrow elliptical, slightly raised, and without rays ; cardinal teeth rather small, 

 compressed, and crenulate ; lateral teeth rather long, curved, lamellar, and rather 

 blunt at the end ; anterior cicatrices distinct, small and deeply impressed ; poste- 

 rior cicatrices distinct and well impressed; dorsal cicatrices placed above the centre 

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

 beaks rather deep and obtusely angular; nacre very white and somewhat iridescent. 



Remarks.— Them are six specimens before me ; four of them have been with 

 me for many years, laid aside for further and better lights; the other two speci- 

 mens were recently received from Dr. Lewis, having been obtained from the Holston 

 Eiver by Miss Law. Neither of these six specimens can be placed in any species 

 with which I am acquainted. In outline this species is perhaps nearest to abacus^ 



