422 THE CHICAGO ACADEMY OF SCIENCES. 
Limnea mighelsi WALKER, Nautilus, XIV, p. 8, 1900; XXI, p. 63, 1907. 
Lymnea emarginata mighelsi WALKER, Nautilus, XXIII, p. 9, 1909. 
Limnea decollata CHapwick, Wis. Nat. H. Soc., IV, p. 80, 1906. 
Limn@a emarginata LAPHAM, Proc. Phil. Acad., p. 155, 1860— BINNEY, 
L. & F. W. Sh, N. A, II, p. 53, 1865 (part)—Sarcent, Nautilus, [X, p. 127, 
1896.—WIswaLL, Nat. Sci. Journ., I, p. 48, 1897-——Baker, Bull. Chi. Acad. Sci., 
II, p. 212, pl. 1, fig. D, 1900; Bull. Chi. Acad. Sci., I], p. 195, 1900 (part).— 
STEARNS, Proc. Nat. Mus., XXII, p. 136, 1900—Cuapwick, Bull. Wis. Nat. H. 
Soc., IV, p. 82, 1906. 
Limnea emarginata LarHaM, Trans. Wis. State Ag. Soc., II, p. 368, 1853. 
SHELL: Solid, rotund, tumid; periostracum, light horn, varying 
to brownish or purplish; sculpture as in emarginata, but growth lines 
coarse, the surface of the shell frequently raised into ridges, sometimes 
giving a malleated aspect; spiral lines rather conspicuous; nuclear 
whorls rather large, rounded, whitish, the outline resembling those of 
catascopium, whorls 5 to 5%, rounded, tumid, the body whorl usually 
very convex ; the whorls increase very rapidly in size and are generally 
strongly angulated on the shoulders of the penultimate and body 
whorl; spire short, tumid, wide; sutures impressed; aperture ovate, 
langer than the spire, rounded and effuse anteriorly, angulated poster- 
iorly ; outer lip with a slight varical thickening within ; inner lip broad, 
reflected, closely appressed to the shell, generally completely closing the 
umbilicus; the parietal callus is very thick and in old shells is raised 
so as to make the aperture continuous ; the columella is much thickened 
and frequently develops a strong plait; axis slightly twisted. 
Length. Width. Aperture length. Width. 
22.50 14.10 14.00 8.50 mill. Lake Houghton. 
23.00 15.00 13.00 iio © cS 2 
21.00 13.50 14.00 toad) ~ = 
19.00 13.00 11.50 iene 3 ae 
18.00 13.50 11.50 SiO Ones * a 
19.00 12.50 12.50 7.00 “ Madison, Wis. 
25.50 15.50 16.00 Sica Pine Lake, Mich. 
23.50 16.00 17.00 8:50) -\ ae = 
20.00 13.00 14.50 (GeO) = ee Y 
Types: British Museum Natural History, London, England. 
Type Locatity: North America. (Probably founded on Michi- 
gan specimens ). 
ANIMAL: Not examined alive. 
Jaw: As in emarginata. 
Raputa: (PI. IX, fig. H.) Formula 3%4 3374+$414+343374+34% 
(31-1-31) ; the teeth are in all respects like those of emarginata. In 
one specimen there were ten instead of nine full laterals, and the transi- 
tion teeth began very abruptly. 
