188 PROCEEDINGS OF THE ACADEMY OF [March, 



Jacob's Canyon, in the second gulch north of Warm Spring Canyon. 

 It was not noticed at Station OS. 



Fig. 1. Alt. 12.8, diam. 23.0, umbilicus 5.9 mm. 



" 2. " 11.8, " 22.3, " 6.1 " 



" 3. " 11.3, " 22.7, " 6.0 " 



" 4. " 12.5. " 21.8, " 6.0 " 



" 5. " 11.8, " 24.0, " 6.1 ." 



(2) At Station 66 (PI. XIII, figs. 6, 7), in the first gulch facing west, 

 north of Warm Spring Canyon, the shells are smaller and usually 

 more elevated, the last whorl at the aperture generally falling well 

 below the lower band. Color and sculpture are normal. 



Fig. 6. Alt. 12.0, diam. 19. umbilicus 5.0 mm. 

 " 7. " 10.5, " 17, " 4.6 " 



(3) In the head of Shinumo Canyon (PI. XIII, figs. 10, 11, 12), 

 Stations 50, 51, 52, the shells are typical in form, but a majority of them 

 have the bands weak, or one or both may be absent (figs. 10-12, 

 Station 50, 5,500 feet elevation). Farther west, at Station 53, the 

 bands are somewhat stronger. Beyond this, going west, the shells 

 are smaller (Stations 54, 55, 56, 57), the last whorl falls more, and the 

 ends of the lip approach — senile characters, doubtless indicative of 

 unfavorable conditions leading to decadence of the race (PI. XIII, 

 figs. 13, 14, "Station 55, at 5,500 feet). 



Fig. 10, diam. 20 mm. Fig. 11, diam. 19 mm. Fig. 12, diam. 

 17.7 mm. (Station 50). 



Fig. 13. Alt. 9.2, diam. 15.7 mm. (Station 55). 



" 14. " 7.8, " 14.5 " umbilicus 4 mm. 



" 15. " 9.2, " 15.7 " 



(4) Moquitch Gulch, Stations 75, 76 (PI. XIII, figs. 16-18). The 

 shells are of medium size, more or less brown, with typical bands. 

 An albino form, white with greenish, translucent bands, appears here. 



Fig. 16. Alt. 11.7, diam. IS, umbilicus 3.9 mm. (Station 76). Fig. 

 17. Diam. 17.3 mm. Fig. 18. Diam. 18.8 mm. (Station 75). 



(5) Continuing southward on Snake Gulch, we encounter snails 

 essentially like those from Stations 49, 50 and 37 in Stations 35, 34, 33. 

 At Station 78, boldly marked two-banded shells and beautiful albinos 

 occur, as already figured from Moquitch Gulch. At Stations 32 and 77 

 most of the shells are large and dark, but a few are small. 



(6) Warm Spring Canyon (PI. XIII, figs. 8, 9). Finely developed 

 shells occur at Stations 59, 60, 61, 62, 64, 65 and 73 or 74, mostly 

 with the normal color-pattern, but sometimes the bands are weak or 

 almost absent, chiefly in shells from Station 61. 



