1906. 



NATURAL SCIENCES OF PHILADELPHIA. 



561 



southwestward. The shells measure 4.5 to 5 mm. diam. and have 

 nearly 5^ whorls. 



At the following places a small race of V. simpsoni occurs. The 

 largest shells are barely 4 mm. in diam., with 5 whorls. The umbilicus 

 is smaller and the aperture less lengthened than in the typical form. 



Missouri: Chad wick. 



Arkansas: Rogers, Hardy, Blue Mountain Station, Petit Jean 

 Mountains, Morris Ferry. 



Indian Territory: Wyandotte, Poteau. 



Vitrea aulaoogyra n. sp. 



vShell similar to V. petrophila but very much larger, with sculpture of 

 close, obliquely radial striae on the upper surface, the striae fine and 

 close on the inner whorls, much coarser on the last; striae and interven- 

 ing grooves about equal. Upper surface slightly convex, nearly flat. 

 Whorls 5^, very slowly widening, the last very much wider, rounded 

 peripherally, the base smoothish, not distinctly striate. Aperture as in 

 V. petrophila. Umbilicus slightly smaller in proportion, one-fourth 

 the diameter of the shell. 



Fig. 4. — V. aulacogyra, X 4. 



Alt. 3.3, diam. 8 mm., umbilicus 2 mm. wide. 



Magazine Mountain, in the talus at the north side of the summit. 



This form evidently stands close to V. petrophila, from which it 

 differs in the close sculpture of all the whorls and the larger size. The 

 maximum diameter of petrophila in the Ozarks, judging from over 30 

 specimens from various places, is 5^ mm., with 5^ whorls, the umbilicus 

 1.6 mm., contained 3^ times in the diameter. The largest Tennessee 

 specimen before us measures 5.6 mm., with 5^ whorls. Bland gives 

 the diameter of petrophila as 6 mm., with 5^ to 6 whorls. 



V. aulacogyra is excessively rare. Only one specimen, perfect though 

 bleached, was found. 



