﻿1^8 I.AMI'SII.IS 



('.roup of Lampsilis Icptodou. 



Shell rather thin, elonj:rate, elliptical, compressed, decidedly 

 [jointed behind, the point raised above the center of the shell ; 

 beaks low, their sculi)ture very feeble; there is a conspicuous 

 post-dorsal wing- in young shells, and sometimes vestiges of 

 an anterior wing; young shell rather dull and faintly rayed; 

 there is a decided anterior basal and posterior gape; hinge 

 teeth very imperfect : pseudocardinals often alniost wanting, 

 even in young shells ; laterals faint, sometimes wanting in the 

 adult shell ; nacre coppery to purplish ; female shell not inflated 

 at post-])ase. Animal having the branchicC large, very thin, 

 light brown, free nearly the wdiolc length of the abdominal sac ; 

 palpi larg-e, thin, nearly semicircular ; mantle thin, with a wide 

 crenulate border; marsupium projecting slightly below the in- 

 ner gills. 



Lampsilis i.eptodon (Rafinesque). 



Shell irregularly long^ ovate, the dorsal line being generally 

 more nearly straight than the basal line, very inequilateral, thin 

 to subsolid, rather compressed, with a low, narrowly rounded 

 posterior ridge, slightly winged behind when young, the wing 

 mostly disappearing in adult shells, gaping at the anterior base 

 and behind ; beaks low, rather compressed, their sculpture con- 

 sisting of a few very faint, doubly-looped ridges ; surface cov- 

 ered with wide, very uneven, often sulcate, growth lines, green- 

 ish, olive-green, or in old shells brownish, with wide, feeble 

 green rays ; epidermis not shining ; there is a very feeble, low 

 tubercle under or in front of the beaks in each valve, but it is 

 sometimes wholly wanting: left valve with the faintest vestige 

 of one or two remote laterals ; right valve with a stronger single 

 lateral ; beak cavities shallow with a row of irregular, large 

 dorsal scars ; anterior adductors long, vertical ; posterior ad- 

 ductors large ; nacre purple, bluish or salmon-color, often 

 clouded. The male and female differ but little ; those of the 

 latter have a slightly fuller base, and the rather sharp posterior 

 point is a little higher than in that of the male. 



Length 117, height 60. diam. 28 mm. 



