THE NAUTIJLUS. 135 
(5.) Patula strigosa Gld. var. intersum. 
Shell umbilicated, subleuticular, depressed, thin, dark horn color, 
more or less stained with darker chestnut. Whorls 53 or 6, some- 
what flattened above, more convex beneath, obtusely carinated at the 
periphery and bearing numerous coarse oblique rib-like striz, and 
two dark revolving bands; suture well impressed; umbilicus large, 
pervious; aperture oblique, subangulated; lip simple, thickened, 
its terminations joined by a thick callus. 
Height of the largest specimen 3 inch, breadth ? inch. 
Height of the smallest specimen 75 inch, breadth 7, inch. 
Habitat. Bluffs along the banks of little Salmon River, Idaho. 
RemMArkKs.—This shell inhabits stone piles at the foot of a steep 
bluff back some distance from the river. It seems to be quite rare 
as I found but few specimens during the two or three days of my 
stay in its vicinity, and many of them were dead. I regard it as one 
of the most interesting shells found by me during the season, for it 
combines the depressed angulated or keeled forms of the Haydeni 
side of the series, with the sculpturing of Idahoensis, two shells 
representing opposite characters in every respect. It thus becomes 
the companion of Wahsatchensis, a beautiful shell combining the 
same characters, but much more developed and connected with the 
large elevated forms. Var. intersum fills the opposite office by 
uniting these characters with the small depressed forms. Taken as 
a whole, this series of shells as now completed, seems to me to offer 
the best guide or key to the study of species that the student can 
have. Every known external character belonging to the genus 
Helix, is so gradually modified and blended with opposite characters, 
that if one had the molding or making of the many and various 
intermediate forms, he could scarcely make the series more complete 
than nature has done herself. 
NOTES ON SOME NORTHERN PUPIDAE WITH DESCRIPTION OF A 
NEW SPECIES. 
BY DR. V. STERKI. 
Vertigo tridentata Wolf. 
Has a wide distribution in the northern part of the country ; 
originally found in Illinois, it has been collected in different parts of 
