The shell is umbilicate, turrited-conic, thin, whitish-corneous, somewhat translucent, with unevenly developed striation, distinct,and close in places, weaker and sparse elsewhere. The summit is decidedly obtuse, as inA. limosa, the first whorl being nearly planorboid; subsequent whorls are evenly, strongly convex. The aperture is very shortly ovate, almost round, its length contained almost 2½ times in that of the shell. Peristome thin, in contrast with the preceding whorl for a short distance.
Length 4.3, diam. 2.7 mm.; 5 whorls (type).
Length 3.75, diam. 2.3, length of aperture 1.35 mm.; 4⅔ whorls.
Length 4.1, diam. 2.75, length of aperture 1.65 mm.; 4⅔ whorls.
Oneida Lake; off Short Point in 8½ ft., mud bottom. Lower South Bay, in 18 ft., on mud bottom.
This species resemblesA. limosain the conspicuously obtuse apex, but differs by the more elevated, turrited spire and the smaller calibre of the whorls, hence smaller aperture. It is also a weaker shell, with more whorls in specimens of the same length.
There is also an abundant smaller form, resembling the typical form in texture, apex and shape of the whorls, varying in form, but relatively broader than the type. There are some intermediate examples, but as Mr. Baker considers it desirable to have a designation for this form, it may be calledA. bakerianaformnimia. The type measures: length 3, diam. 2.5, length of aperture 1.4 mm.; 4 whorls.