Amnicola oneida, n. sp.
The shell is typically more slender than A. lustrica, turrited-conic, narrowly umbilicate, corneous, minutely striate. The apex is slightly obtuse, but the first whorl projects visibly, as in lustrica, whorls very convex, parted by a deep suture. The aperture is ovate, small, its length contained more than 3 times in that of the shell; upper extremity narrowly rounded. The peristome is continuous, thin, very briefly in contact with the preceding whorl above.
Length 4, diam. 2, length of aperture 1.25 mm.; 6 whorls.
Lower South Bay, Oneida Lake, N. Y., collected by F. C. Baker, 1916.
This species is typically narrower than A. lustrica Pils., with a smaller aperture and shorter whorls; but it is chiefly distinguished by the more convex whorls (deeper suture), and the rounded instead of angular posterior end of the aperture. In Paludestrina nickliniana the last whorl is much longer. Possibly it may be a subspecies of lustrica, yet it has so distinct an appearance that a special name seems desirable. There are also wider examples, which still differ from lustrica by the deeper suture and aperture.