308 NEW UNIONID^, MELANID^, ETC., 



Shell smooth, elliptical, somewhat compressed, inequilateral, rounded before and 

 behind; substance of the shell somewhat thick, thicker before; beaks slightly 

 prominent, undulate at the tips ; ligament short, thick and dark brown ; epidermis 

 dark brown, squamose towards the margin, without rays and with somewhat distant 

 marks of growth; umbonial slope fiat and rounded; posterior slope narrow elliptical, 

 slightly carinate, with two slightly impressed lines in each valve from the beaks to 

 the posterior margin ; cardinal teeth rather thick, raised, compressed, corrugate and 

 double in both valves; lateral teeth long, lamellar and somewhat curved; anterior 

 cicatrices distinct, rather large and well impressed; posterior cicatrices confluent, 

 large and very slightly impressed ; dorsal cicatrices placed in the centre of the 

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

 and obtusely angular ; nacre purple and very iridescent. 



Remarlcs. — This species is closely allied to Ptjlasii (nobis), but may be 

 distinguished by being larger and of a more regular ellipse. Among the specimens 

 before me two are adults, one of which is figured. They all have a deep purple nacre 

 in the cavity of the shell, the anterior and basal margins near to the edge being 

 white. One of the specimens has a tinge of salmon color towards the basal margin. 

 There are no rays on either of these specimens, except quite a young one, which has 

 obsolete rays ; and the tips of the beaks present minute undulations. The inferior 

 posterior cicatrix is larger than usual in proportion to the superior one. It is with 

 great pleasure I name this species after Prof. Cope, who, while exploring the head- 

 waters of the Holston, New and Catawba Rivers for ichthyological purposes, 

 extended his researches to the Molluscs of these little-frequented districts, among the 

 mountains of Virginia, North Carolina and Tennessee. 



Unio cylindrellus. pi. 48, fig. 121. 



Testa Ijevi, late elliptica, cylindracea, valde inrequilaterali, antice et postice rotundata ; valvulis 

 subcrassis, antice crassioribus ; natibus promioulis ; epidermide luteola, eradiata; dentibus 

 cardinalibus parvis, subconicis corrugatisque ; lateralibus longis subcurvisque ; margarita intus 

 purpurea et valde iridescente. 



Shell smooth, widely elliptical, somewhat cylindrical, very inequilateral, rounded 

 before and behind; valves somewhat thick, thicker before ; beaks slightly promi- 

 nent; epidermis yellowish, without rays; cardinal teeth small, subcorneal, corrugate; 

 lateral teeth long and somewhat curved; nacre purple within and very iridescent. 

 Proc. Acad. Nat. Sci. 1868, p. 144. 



Hah. — Duck Creek, Tenn., Swamp Creek, Whitfield Co., Geo., Major Downie, and 

 North Alabama, Prof. Tuoraey. 



My cabinet. 

 Diam. -7, Length -8, Breadth 1-5 inches. 



