150 



THE CHICAGO ACADEMY OF SCIENCES. 



with three cusps, of which the central one is very long and the 

 side cusps are (generally) subbbsolete, the cutting points well 

 developed; lateral teeth similar to the central tooth, but with 

 side cusps distinct; marginal teeth with a small base somewhat 

 quadrangular in shape, and with irregularly shaped cusps, the 

 inner being several times longer and broader than the outer 

 cusp; both have well developed cutting points. The transition 



FIG. 19. 



Radula of POLYGYRA PROFUNDA Say. (Original.) c, central tooth; 

 1, first lateral; 18, intermediate lateral; 22, 27, 28, 32, marginal teeth. 



from lateral to marginal teeth is very gradual, and it is diffi- 

 cult to determine just where one set ends and the other begins 

 (Fig. 19). Several teeth in one membrane examined (37-1-37) 

 had the inner cusp bifid (27-32 in figure). Mr. Binney says: 

 "but the change from laterals to marginals is very gradual, 

 being made without splitting of the inner cutting point, which 

 is simple on the extreme marginals even."* 



This membrane was undoubtedly a pathological specimen. 

 There are over 120 rows of teeth. 



Gcnitalia: "The penis sac is not very stout, long, receiv- 

 ing the retractor muscle at about the middle of its length, and 

 tapering very gradually towards its summit into the vas defer- 

 ens; genital bladder large, globose-oval, on a long, narrow 

 duct." (W. G. Binney.) 



Distribution: Western New York to Minnesota, south to 

 Virginia and Mississippi. 



Geological distribution:. Pleistocene; Loess. 



Habitat: Found in large numbers in woodlands where 

 there is moisture, under dead underbrush and old logs. 



*Manual Amer. Land Shells, p. 318. 



