282 MEMOIRS OF THE CARNEGIE MUSEUM. 



Genus Lampsilis Rafinesque (1820). 

 Ortmann, 1912, p. 345; Simpson, 1914, p. 35. 



Type Unio ovatus Say. 

 In Pennsylvania I distinguish seven species and three varieties, which are to 

 be recognized as follows: 



Key to the Species and Varieties of Lampsilis. 

 Oi. Shell subelliptical, elongated, considerably over one-and-a-half times as long as high. 



bi. Shell more or less swollen; in the female greatly inflated and broader behind. Epidermis more 

 or less smooth and shining, with the rays, when present, rather sharply defined, 

 fi. Larger, greenish-yellow, with dark rays, colors bright. Growth-lines irregular and not 



very distinct L. luteola. 



C2. Smaller, pale yellowish, or pale brownish, rays not so dark, colors duller. Growth-lines 



generallj' distinct and regular L. luteola rosacea. 



b-i. Shell more or less compressed, in the female not so greatly inflated and broadened behind. Epi- 

 dermis rough, and not shining, with the rays less sharply defined L. radiata. 



2- Shell suboval or subeUiptical, not elongated, rarely about one and a half times as long as high, gen- 

 erally shorter. 

 6i. Shell moderately thick, or even comparatively tliin. Color of epidermis yellowish, greenish, 

 or grayish olive, or dull brownish. Rays variable, but, when present, generally sharply 

 defined. 

 Ci. Epidermis yellowish or greenish olive, more or less shining (dull only in old shells). Rays, 

 when present, more or less sharply defined. 

 du Epidermis more or less greenish, more or less shining; when yellowish, the rays cover 

 most of the shell, 

 ei. Rays absent or simple, broader or narrower, not much crowded. Shell rather 

 large, 

 /i. Shell larger, colors brighter, rays more sharply marked, when present, and 

 rather dark. 

 Qi. A sharp posterior ridge present, and posterior slope truncate. .. .L. ovata. 

 g2- No sharp posterior ridge, posterior slope not truncate. 



L. ovata veniricosa. 

 /o. Shell smaller, colors duller and paler, raj's less distinct and not very dark. 



L. ovata canadensis. 

 €2- Rays always present, fine, rarely somewhat broad, much crowded, and more or 



less interrupted or wavy. Shell of smaller size L. fasciola. 



di. Epidermis bright yellow (wax-yellow), sometimes inclining to reddish brown, very 

 bright and glossy. Rays, if present, very distinct, but generally restricted to the 



posterior part of the shell L. cariosa. 



Co. Epidermis dull in color, grayish olive, not very shining. Rays ill-defined L. ochracea. 



bi. Shell very thick and heavy. Color of epidermis more or less reddish-yellow or brown. Rays 

 indistinct L. orbiculata. 



