324 THE CHICAGO ACADEMY OF SCIENCES. 
eral has seven to nine cusps, all large, and the outer lateral has 
eleven small cusps. All the teeth seemed to have well devel- 
oped cutting points (Fig. 165, Mus. no. 12770). 
Genitalia: Notexamined, but external appearance as in 
subulare. ‘ 
Distribution: Lake Michigan, Ohio, Indiana, Illinois, Ken- 
tucky, Tennessee. 
Geological distribution: Pleistocene; Loess, 
Habitat: Found in rivers and ponds, in more or less clear 
water, on a sandy bottom. Does not like a muddy habitat. 
Remarks: This species is distinguished from sudulare by 
its very pronounced peripheral carina and flat-sided whorls. It 
A 3 
Fie. 115. 
Radula of PLEUROCERA ELEVATUM Say. (Original.) C, central 
tooth; 1, intermediate tooth; 2, 3, lateral teeth. 
also attains a much larger size. When browsing on the glass 
side of an aquarium, e/evatum thrusts out its rostrum to its full- 
est length, the tentacles are drooped and it slowly proceeds 
in this manner, the radula being plainly seen in action at the 
endof the rostrum. This species does not seem to be as com- 
mon in individuals as sudulare. It has been found fossil in a 
cellar on the corner of Sheffield and Lincoln avenues. 
131a. Pleurocera elevatum lewisii Lea, p)]. xxxv, figs. 5-6. 
Trypanostoma Lewisit LEA, Proc. Phil. Acad., p. 172, 1862. 
Shell: Differing from the typical form in being strongly 
striate, the strie being raised into heavy ridges. The form is 
also heavily banded with brown, and the satures are strongly 
impressed. 
Length, 27.50; width, 10.00; aperture length, 8.00; width, 5.00 mill. (8745.) 
. 27,0052" 0) e 8:003'5, (f° °F ARG Fer (BT4R.) 
i 39.00; 15.00; 6 ARO tO ae He eee aa) 
i ZtOOy ee 13.00; . Oo EDs, ho SOOT Ser el eee 
