396 



PROCEEDINGS OF THE ACADEMY OF 



[June; 



are conspicuous characters. The smaller umbilicus and less de- 

 pressed contour separate it from S. santaritana, which also differs 

 more fundamentally by its genitalia. S. walkeri is very much like 

 S. clappi in soft anatomy. Its relation to S. huachucana Pils. 

 remains to be defined when that species shall have been dissected. 

 Measurements of the organs in mm. follow. 



Sonorella walkeri aguacalientensis n. subsp. PI. IX, figs. 5, 5a, 5b, 6, 6a, 66. 



A form with the shell not constantly distinguishable from S. 



ivalkeri was found in some abundance at Stations 1 and 2, in the 



mouth of Agua Caliente 

 Canyon. Station 1 is in 

 rocks on the bank of the 

 wash running out of the 

 canyon, immediatelj' 

 southeast of the fine 

 spring of tepid water 

 which gives this canj^on 

 its name. This is the 

 lowest Station for anj^ 

 snail found in these 

 mountains, the elevation 

 being about 3,800 feet. 

 All of the alcoholic speci- 

 mens of this lot were lost 

 after leaving the moun- 

 tains, so that the ana- 

 tomical characters are 

 unknown. The shells 

 measure 19 to 24 mm. in 

 diameter and live in 



crevices or under fragments of a friable, shale-like rhyolite, of a dark 



vinaceous-drab color. See PI. IX, figs. 6, 6a, db. 



Fig. 5. — Genitalia of S. w. aguacalientensis, Sta- 

 tion 2, with detail of penis-papilla (pp.). epi., 

 epiphallus; p., penis; vag., vagina; v.d., vas 

 deferens. 



