THE NATURAL HISTORY SURVEY. 147 
The teeth are like those of #identata, excepting that there are 
eleven perfect laterals, and all the inner cusps are simple until 
the seventeenth marginal, which is bifid. Binney (Manual, 
p. 292) gives 40-I-40 teeth with twelve perfect laterals. The 
writer is certain that his count was correct, as the teeth were 
recounted several times, always with the same result. The 
membranes were perfect (Fig. 17). 
Fia. 17. 
Radula of POLYGYRA FRAUDULENTA Pilsbry. (Original.) c, cen- 
tral tooth; 1, first lateral; 10, outer lateral; 15, first marginal; 16, 20, mid- 
dle and outer marginals. 
Genitaha: Similar to that of #identata,.but ‘the duct of 
the genital bladder is of equal size throughout its length—an 
unimportant, even if a constant difference.” (Binney.) 
Distribution: Ontario, Canada, to Michigan and Illinois, 
south to Georgia. (Pilsbry.) 
Geological distribution: Pleistocene; Loess. 
Habitat: Same as tridentata, and frequently associated 
with that species. 
Remarks; This species has long been known under the 
name “fallax Say,” but Professor Pilsbry has shown (I. ¢c., p. 21), 
that this is not the true fa//ax of Say, that species being the 
introferens of Bland. It is easily distinguished from ¢ridentata 
by its elevated spire and strongly armed aperture, and is more 
common than that species. The animal is very timid in cap- 
