250 PROCEEDINGS OF THE ACADEMY OF [1893. 



Now and then one is found with a small shell, rapidly increasing last 

 whorl and comparatively large aperture, strongly recalling similar 

 examples of Helix thyroides Say. The whorls are, as a rule, 3^-3? 

 in number, and only the largest shells have 4 or nearly so. There 

 is some variability in the size and shape of the umbilicus, being in 

 some nearly as in excentrica, while in others it is almost regular or 

 funnel-shaped ; yet a marked widening near the aperture is almost 

 always found. 



It has been accepted as a character of pulchella that the last 

 whorl does not descend at the aperture. This is only approximately 

 true because while not in such a degree as in some other species, 

 the last whorl descends distinctly, especially at the suture, in 

 about one- third or one-fourth of the specimens from different places in 

 Europe and North America. The last whorl, moreover, slightly 

 ascends more at the back than at the suture, and specimens are even 

 found with the last whorl first ascending and then descending 

 slightly but distinctly at the suture, a character which is found more 

 constant and more marked in V. cyclophorella, tenuilabris and 

 others. 



There is some variation also in the size and shape of the lip ; it is 

 almost typically stronger in the upper outer part, so as to modify 

 the shape of the actual aperture, as shown in Man. Conch., PL 32, 

 figs. 3 and 5, the same as in V. costata, fig. 22, and pulchelhila 

 Hde., fig. 53. In the upper part also the lip often protrudes 

 beyond the margin, and specimens are not uncommon where the 

 strong lip projects on the whole circumference, except at the ends 

 (fig. 4). While fresh shells are usually of pale horn color and trans- 

 parent, some may be found whitish or milky opaque. I found a 

 colony of about a hundred exclusively so colored some years ago, in 



Average. Largest. Smallest. 



Aargau, Switzerl. (drift) 2 3 25 21 



Lyons, France (the largest) 2 - 5 2'7 2*3 



Madeira 2*4 2d 23 



Washington, D. C 23 24 22 



Saco, Maine (2 examples, only) 22 22 22 



Quebec, Canada 23 2.4 21 



Brantford, Ontario 24 25 22 



Tremont, Pa 24 26 22 



New Philadelphia, Ohio 23 26 21 



Joliet, 111 24 25 20 



Iowa City, Iowa 2'4 26 22 



Greenville, Tenn 23 2"4 21 



San Jose, Cal. (greenhouse) 2"3 24 21 



Mauritius 23 2'4 23 



