350 THE CHICAGO ACADEMY OF SCIENCES. 



Radula: Similar to that of sincera. 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 strongly tricarinate. The vari- 

 ation, however, does not seem to be confined to any particu- 

 lar locality and for this reason the names given to the 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 

 e gg- When hatched, the young are very active and float shell 

 downwards on the surface of the water. Egg laying extends 

 from March to July. Tricarinata is widely distributed in the 

 area but is most common in Lake Michigan. 



145. Valvata bicarinata Lea. Unfigured. 



Valvata bicarinata LEA, Proc. Amer. Phil. Soc., Vol. II, pp. 81, 83, 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- 

 inae 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 carinae, continuous as in tricarinata; base keeled; 

 umbilicus widely opened. 



Length, 3.50; width, 5.00; aperture length, 2.00; width, 2.00 mill. (12365.) 

 3.00; " 4.00; " " 2.00; " 2.00 " (12365.) 



3.50; " 5.00; " " 2.00; " 2.00 " (12366.) 



Animal: The animal of bicarinata differ considerably from 

 that of tricarinata. 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- 



