2 University of Michigan 



may easily have been identical with the type locality of the 

 subspecies. 



About 125 specimens varying from shells of only a few 

 whorls to fully adult specimens of a little over five whorls 

 compose this series. The illustration accompanying Dr. 

 Bartsch's paper evidently shows a shell not quite mature, as 

 fully grown shells have about one-half whorl more, and the 

 ends of the peristome united by a heavy callus. Measure- 

 ments of thirty-six fully adult specimens yield the following 

 figures : 



Greater diameter 12.1, lesser ii.i mm., alt. 8.16, Index A/D, 

 67.35 average for 36 shells. 



Greater diameter 14.2, lesser 13.0 mm., alt. 9.6, Index A/D, 

 67.60 largest in diameter. 



Greater diameter ii.o, lesser 10.8 mm., alt. y.y, Index A/D, 

 70.00 smallest in diameter. 



Greater diameter 11.5, lesser 11.2 mm., alt. 9.7, Index A/D, 

 84.34 most elevated. 



Greater diameter 12.3, lesser ii.o mm., alt. 7.0, Index A/D, 

 56.91 most depressed. 



Variation in diameter from 14.2 to 11, or 3.2 mm. 



Variation in altitude from 9.7 to 7, or 2.7 mm. 



Several features correlated with age variation are apparent. 

 In young shells the sculpture of the early whorls is very dis- 

 tinct, consisting of raised spiral lines noticeably stronger after 

 the nuclear one and one-half whorls. Shells of three or four 

 whorls tend consistently toward a less elevated form than ma- 

 ture shells, a diflference correlated with the sudden descent of 

 the last whorl or half whorl to the aperture. In some speci- 

 mens the descent has been so sudden that the peristome par- 

 tially conceals the umbilicus and is placed almost directly be- 

 low the preceding whorl. One of the specimens figured (figs. 



