26 : VIVIPARA. 
Length 32, diam. 20 mill. 
Ohio, Michigan, Western New York. 
This species much resembles a half-grown 
ponderosa, but is more regularly oval in its 
outline and of lighter texture. There is no 
doubt of its being perfectly adult, and it is, I 
believe, a very good species, with characters 
intermediate between V. ponderosa and V. in- 
tegra. 
"a, Shell geniculate. 
14. VIVIPARA GENICULA, Conrad. 
Hald., p. 15, t. 5. 
This species is very widely distributed in 
the far southern States, and seems nearly to 
replace V integra and decisa. Mr. W. G. 
Binney suggests that it is a deformed decisa, 
but I have seen numerous specimens from 
many localities, and they present a uniformity 
of appearance that can be due to nothing less 
than specific force. 
(52) 
wat rh eae 
