New Fresh-Water Shells. 329 
ANCYLUS FUSCUS. 
Plate III. Fig. 17. 
A. testa tenui, sub epidermide pellucida, subdepressá, ellipticá ; epi- 
dermide fuscA, crassá, asperá, extra marginem prominente ; apice ob- 
tusà, ad dextram, vix posterà. 
Shell thin, transparent Sel the blend not 
much elevated, elliptical, moderately curved at the 
sides ; epidermis brown,. visible through the shell, 
giving it the appearance of having the same color, 
thick, rough, slightly extending beyond the margin 
of the shell; apex obtuse, moderately prominent, 
scarcely hahbed the middle, inclining © to the right, so 
as to have only two-fifths of the width on that side. . 
Length, 3l inch ; Nt. .22 inch ; height, .05 
inch. 
Cabinets of, Bost. Pes Nat. Hist. ; í ee Mr. Kinne 
Prescott, of Andover; and my own. 
Habitat and station. This species was found ad- 
hering to stones, in a small rivulet, at Andover, by 
Mr. Kinne, Prescott, to whom I am indebted for 
many interesting species of t It has also been 
found at Mansfield. 
Remarks. This species is ah, distinguished by 
its epidermis. The A. rivularis, Say, differs also in 
being much more narrow, having its sides straight, 
and its apex more acute, and A. tardus,* Say, i is 
more elevated, and in both of these the apex does not 
incline so far to the right as in our species. "The A. 
lacustris, Drap., is more narrow; with an apex more , 
This s species, hitherto unknown in New England, occurs quite 
Piles: in a rivulet in Middlebury, Vt. ý 
VOL. III. — NO. Il. ; . 
