334 THE CHICAGO ACADEMY OF SCIENCES. 
gait. It is widely distributed throughoutthearea. At several 
points in Chicago it has been found among Pleistocene fossils. 
134a. Amnicola limosa parva Lea, pl. xxxi, fig. 11. 
Amnicola parva LEA, Proc. Amer. Phil. Soc., Vol. II, p. 34, 1841; 
TrRyON, Con. Haldeman’s Monograph, pl. xvii, fig. 2. 
Shell; Smaller than typical /zmosa, the whorls shouldered 
and tumid below the suture. Otherwise like mosa. 
Length, 3.50; width, 2.75; aperture length, 2.00; width, 1.50 mill. (10218.) 
js S200 4 8 200s f aes 5, | en Ng age 2 ON (10218.) 
Animal and Dentition: Same as /imosa. 
Distribution: Atlantic and Middle States. 
Geological distribution: Pleistocene. 
Flabitat: Same as limosa. 
Remarks: This form is found at Joliet, Salt Creek and 
Berry Lake; the writer has admitted it to varietal rank for the 
reason that it seems to be always recognizable, although it is 
apparently only a stunted form of “mosa. It is not common. 
134b. Amnicola limosa porata Say, pl. xxvi, fig. 13. 
Paludina porata Say, Journ. Phil. Acad., Vol. II, p. 174, 1821, 
Amnicola orbiculata LEA, Proc. Amer. Phil. Soc., Vol. II, p. 34, 1841. 
Shell differing from dmosa in being generally widely um- 
bilicated, in the whorls being more swollen and the spire 
shorter. 
Length, 5.00; width, 4.00; aperture length, 2.80; width, 2.10 (13357.) 
y: 5.00; “4.50; be Ao. ae 2.05 (18357.) 
This variety is the most common and is universally dis- 
tributed. 
135- Amnicola lustrica Pilsbry, pl. xxvi, fig. 12. 
Amnicola lustrica PILSBRY, The Nautilus, Vol. IV, p. 53, 1890 (not A. 
lustrica SAY—Pomatiopsis lapidaria SAY). 
Shell: Narrow (for the genus), thin, translucent; color 
waxy, light brownish or greenish; surface smooth and shining, 
lines of growth very fine, but distinct when viewed with a lens; 
sutures very deeply impressed; spire elevated, conical; whorls 
five, rounded, regularly increasing in size; aperture roundly 
ovate, slightly angled above, waxy inside; peristome continu- 
ous, thin, appressed to the body whorl only for a short distance 
near the upper terminations; base broadly rounded, with a 
narrow and deep umbilicus. Operculum similar to that of 
A. limosa. | . 
