THE NAUTILUS. 9 
Polita cumberlandiana: upper three figures. 
Vitrea pilsbryana: lower five figures, two at the right being 
immature shells, to show teeth of the neanic stage. 
VITREA (PARAVITREA) PILSBRYANA, D. 8p. 
Shell widely umbilicate, elevated, convex above, flattened be- 
low, thin, translucent, highly polished when immature but be- 
coming more opaque and yellowish in adults, light horn color, 
sculptured with unequally spaced radial grooves stopping at the 
periphery which is rather high; suture well impressed; whorls 
about 8 very closely coiled and slowly increasing, the last flat- 
tened above and below; lip simple very slightly reflected where 
it joins the columella, ends united by a thin callus; umbilicus 
wide, contained a little more than 3 times in the diameter of 
the shell, and showing all of the apex. 
There are 3 or 4 pairs of large, tubercular, sometimes slightly 
oval teeth, visible thru the base of the shell at all stages of 
growth and in immature shells the upper teeth are visible from 
above. Theupper teeth, which are slightly below the periphery, 
are the larger, more elevated and round at thetop. The lower 
teeth are about centrally located on the base and are flattened 
