306 THE CHICAGO ACADEMY OF SCIENCES. 
parts; aperture as large as the shell, rounded; peristome sim- 
ple, entire, acute; color greenish-horn. 
Length, 6.00; width, 4.00; height, 3.00 mill. 
Animal; Not examined. 
Faw: Not examined. 
Radula: Not examined. 
Genitalia: Not examined. 
Distribution: Same as rivularis. 
Geological distribution: Pleistocene. 
Habitat: Similar to vtvularis. 
Remarks: This species is wider and more conical than 
vivularis, and the apex is more central and of directed later- 
ally. Itseems to be very rare and has been found only in the 
DuPage River. ° 
124. Ancylus shimekii Pilsbry, pl. xxxi, figs. 9, 10. 
Ancylus obliqguus, SHIMEK, Bull. Lab. Nat. Hist. Univ. of Iowa, Vol. I, 
Nos. 3, p. 214, pl. iii, figs. 58, 5b, 5¢, 1890. (Preoceupied.) 
Ancylus shimekii PILSBRY, The Nautilus, Vol. IV, p. 48, 1890. 
“Shell: Elevated, thin, transparent, horn-colored, with a 
yellowish-brown epidermis; aperture ovate, conspicuously wider 
anteriorly,in many (especially young) specimens slightly reni- 
form by a barely perceptible incurving of the right margin, 
the anterior, left and posterior margins regularly rounded, the 
right slightly incurved, straight, or but slightly convex; apex 
somewhat acute, elevated, strongly deflected posteriorly and 
to the right, and curved downward, in most specimens quite 
overhanging the posterior right margin of the shell; the apical 
portion of the shell (one-half or more) is strongly laterally, or 
rather, obliquely, compressed, a character which makes the 
young appear proportionally much narrower than the adults; 
the anterior slope of the shell is long and strongly convex, the 
posterior being short and concave. The surface is marked by 
fine lines of growth.” (Shimek.) 
Length,3.50; width, 1.80; height, 1.50 mill. (Shimek.) Large specimen. 
6. DOs ee ees «1.20 “ (Shimek.) Average measurement. 
6. ay LO sa ana Oe “- 110 “ Joliet specimen. 
Animal: “Uniform bluish-white color; the foot is ovate, 
wider anteriorly, and rather narrow for an Ancylus.”’ (Shimek.) 
Radula: ‘Rather narrow, the dental formula being 12-1- 
12.” (Shimek.) 
Distribution: Five miles east of Lincoln, Neb., in Dead 
