THE NAUTILUS. 



9 



Polita cumber la ndiana: 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, n. sp. 



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. The upper teeth, which are slightly below the periphery, 

 are the larger, more elevated and round at the top. The lower 

 teeth are about centrally located on the base and are flattened 



