332 PROCEEDINGS OF THE ACADEMY OF [May, 



4 mm., the lower margin of this band irregular, often producing a 

 "clouded" effect, and a broad white band around the umbilicus, 

 such as sometimes occurs around the umbilicus of strongly albo- 

 fasciated types of cooperi and depressa; 13 grade almost insensibly 

 from the albofasciata form to the binneyi form. Frequently a narrow 

 white band occurs just below the suture, and the upper edge of the 

 white peripheral band is exposed well up the spire, of the higher- 

 spired albofasciata specimens. Transverse ribs average about two 

 to the millimeter, rather irregular, growth lines showing in the 

 interspaces and microscopic spiral striae on the ribs and in the inter- 

 spaces. The color bands are very dark, often forming a striking 

 contrast with the white peripheral and umbilical bands. Diameter 

 15 to 19 mm. (PI. XVII, fig. 2.) 



Sta. 30, southeast of Sta. 29, directly opposite the power plant 

 dam at the entrance to the gorge, at base of Paleozoic limestone 

 rocks on the lower slope of the mountain, where the vegetative 

 cover is poor and rock slide absent or unexposed. Form multicostata, 

 banding weak or absent, ribbing pronounced, diameter 12 to 16 mm., 

 mostly dead specimens, the slope having been very recently burned 

 over. (PL XV, fig. 2.) 



Sta. 31, farther up the slope, at a heavy, steep limestone ledge, 

 beneath a decumbent species of polygonaceous plant which clings 

 closely to the rock. Form multicostata, abundant, much smaller than 

 at Sta. 30, most examples with a narrow and often faint subperipheral 

 color band, and some with a similar band just above the periphery; 

 diameter of adults from 8 to 12 mm., altitude extremely variable 

 (PL XV, fig. 3). The snails increase in size again a hundred feet 

 farther up the slope. Stations 30, 31 and 32 form practically a 

 continuous colony, which we separated into stations merely because 

 of the astonishing difference in size within a short distance. Our 

 observations upon this genus lead us to observe that any given 

 species is likely to vary greatly in size with variation in cover. We 

 also found here 97 Pupilla blandi (Morse) and 5 Vallonia cyclo- 

 phorella Ancey and V. sonorana Pils. 



Sta. 32, at the base of a limestone cliff above Sta. 31, where the 

 vegetative cover is better and the cliff affords considerable shade. 

 Forms albofasciata and binneyi, intergrading as at Sta. 29, except 

 that few are so pronouncedly of the albofasciata type as at 29. Diame- 

 ter from 9 to 16 mm. 



Sta. 33, ravine that cuts back into the east bluff of Bear River 

 valley, just below Wheelon, Box Elder County, probably not a great 



