﻿LAMPSII^IS 97 



Group of Lompsilis nasiita. 



Shell elongated, thin, compressed, with a distinct posterior 

 ridge, and drawn out to a long, pointed beak behind ; epider- 

 dermis rather dull, olive-green, and feebly rayed ; beaks low. 

 sculptured with fine, close-set ridges, which are slightly looped 

 in front and are parallel with the axis of the shell behind ; 

 hinge teeth delicate and compressed ; nacre bluish ; female shell 

 not greatly produced in the post^basal region. Animal with 

 the marsupium often occupying the greater part of the length 

 of the outer gills posteriorly ; inner gills free or united to the 

 abdominal sac. 



Lampsilis nasuta (Say). 



Shell elongated, subcompressed, thin to subsolid, with a well- 

 developed posterior ridge which is usually curved down in the 

 middle; rounded in front; full at the base just behind the cen- 

 ter, and drawn out to a long point behind midway up the height 

 of the shell ; beaks low, sculptured with fine, close ridges, which 

 are looped in front and nm parallel with the axis of the shell 

 behind ; surface having irregular growth lines, and sometimes 

 having a few nearly vertical ribs below the posterior ridges ; 

 scarcely shining, dark olive to brownish or tawny, often faintly 

 rayed, especially when young ; left valve with a sort of double, 

 compressed pseudocardinal and two delicate, nearly straight 

 laterals; right valve with one compressed pseudocardinal, a 

 faint one above it, and a lamellar lateral ; beak cavities shallow, 

 with a row of dorsal scars visible ; muscle scars shallow, the 

 posterior indistinct ; nacre bluish-white, lurid, flesh-tinted or 

 purplish. Female shell with a long marsupial swelling just be- 

 hind the center, not differing greatly from that of the male. 



Length yy, height 35, diam. 18 mm. 



St. Lawrence drainage ; streams flowing into the Atlantic 

 south to North Carolina. 



Type locality, Delaware and Schuylkill Rivers. 

 Unio nosutus Say, Nich. Encyc, ist ed., 1817, pi. iv, fig. i. — 



SwAiNSON, Zool. 111., 1st sen, L 1821, pi. LVir. — Conr.\d, 



Monog., IV, 1836, p. 38, pi. xviir, fig. i, part. — Gould, Inv. 



