Mollusca of Middlebury, Vt. and Vicinity. 267 



rarely in Lake Champlain. Deshayes could not have suggested, 

 as he has, (2d edit. Lam. An. sans Vert, in loc.) that this is the 

 young of P. ponderosa, Say, had he seen suites of young and 

 old in both species. This species is more nearly related to P. In- 

 tegra, Say, from which it is well distinguished by Haldeman, 

 (Monog. Limniad. No. 1.) 



P. lustrica, Say. This species is very abundant in Lake 

 Champlain and in the streams. Its color varies from brown to 

 green in different localities. 



Valvata. 



V. tricarinata, Say. Abundant in Lake Champlain, of a grass 

 green color. 



F. si?icera. Say. This species occurs plentifully in Putts's 

 swamp, on the New York side of Lake Champlain, opposite Brid- 

 port. It is so rare, that a description of the animal may not be 

 without interest. 



Foot whitish, swelling and regularly rounded posteriorly, with 

 the anterior lobes sharply angular, somewhat contracted in the 

 middle, less than .3 in. long ; head anteriorly obtuse and bilobed, 

 — lobes regularly rounded, — whitish, with a tinge of slate color 

 on the top, deepening posteriorly ; mouth pale-yellowish ; tenta- 

 cles filiform, whitish, more than .2 in. long ; eyes minute, black, 

 shining, situated on the upper and outer part of the posterior side 

 of the protuberance at the base of the tentacles ; branchial cavity 

 blackish brown on the margin ; plumose branchia consisting of a 

 stem, on each side of which extend, at right angles to it, about 

 ten filiform obtuse branches, bent in zigzag, shorter near the top, 

 the whole appearing like a feather ; tentaculiform branchia rather 

 longer than the tentacles, equally slender and obtuse. 



LlMN^A. 



L. megasoma. Say. This large and rare species I have seen 

 only at Burlington. 



L. appressa, Say. This species has been found only in or 

 near Lake Champlain. At Burlington it is common. Sometimes 

 it is nearly as much shouldered on the body whorl as the L. stag- 

 nalis of Europe, from which it differs very slightly. 



L. gracilis, Jay. This very remarkable species occurs in Lake 

 Champlain. About half a dozen specimens wese discovered near 

 Burlington, and have been distributed by Prof Benedict. A sin- 

 gle specimen, large and perfect, but without the animal, I found 



