350 THE CHICAGO ACADEMY OF SCIENCES. 
Radula: Similar to that of stacera. The writer could dis- 
cover no differences of importance. 
Distribution: New England to Iowa, Michigan and Mani- 
toba. 
Geological distribution: Pleistocene; Loess. 
Habitat: Same as sincera. 
Remarks: This very distinct species is easily known by 
its elevated, tricarinate whorls. It is very variable, and occurs 
from barely unicarinate to very stronglytricarinate. The vari- 
ation, however, does not seem to be confined to any particu- 
lar locality and for this reason the names given tothe different 
degrees of carination cannot stand, except as varieties. 
This species lays from ten to thirty eggs of a green color, 
and about fifteen days are required for the development of the 
egg. When hatched, the young are very active and float shell 
downwards on the surface of the water. Egg laying extends 
from: March to July. TZvicarinata is widely distributed in the 
area butis most common in Lake Michigan. 
145. Valvata bicarinata Lea. Unfigured. 
Valvata bicarinata LEA, Proc. Amer. Phil. Soc., Vol. II, pp. 81, 85, 1841 
WALKER, The Nautilus, Vol. XV, p. 122, fig. 6, 1902. 
Shell: Depressed, solid, orbicular; horn-colored above 
and whitish beneath; surface shining, lines of growth distinct; 
apex large, horn-colored; spire much depressed, flattened; 
whorls three and one-half to four, rapidly increasing; the car- 
inz are normally two in number, but a third is frequently de- 
veloped; one carina encircles the shoulders of the whorls and 
one the middle of the base, the periphery being sharply 
rounded; sutures pronounced; aperture rounded, angled more 
or less by the carinz, continuous as in “#vicarinata,; base keeled; 
umbilicus widely opened. 
Length, 3.50; width, 5.00; aperture length, 2.00; width, 2.00 mill. (12365.) 
. 3.00; “ 4.00; ‘6 BUD FONTS (12365.) 
“t 3.50; “ 5.00; - ~ J | edibeageeer Ft Ebr, (12366.) 
Animal: Theanimal of d¢carinata differ considerably from 
that of “#carinata. Dr. Lea described the animal as follows: 
“Body rather short and white, head large, tapering, slightly 
enlarged at the anterior termination, with a black mark pass- 
ing from the neck between the eyes, tapering off and reaching 
nearly to the end of the snout, where there are two oblique 
black marks bordered in front by white, and accompanied be- 
