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. 
Sta- : | Penis- Epiphal- Flagel- : Sperma- 
tion. | Penis. papilla. lus. lum. Vagina. theca 
| | and duct. 
5 4.7 2.0 5 1 Sl on ae er 
5 5 3 5 Minute 77 hee 
8 4 2.3 6 i 10~. lana 
15 4.3 2.8 1.3 Se 1Oa eee 
3 4 3 6.5 iW eed Ree piste 
7 5 6.7 Minute y ena Re 
Sonorella walkeri aguacalientensis n. subsp. PI. IX, figs. 5, 5a, 5b, 6, 6a, 6b. 
A form with the shell not constantly distinguishable from S. 
walkeri was found in some abundance at Stations 1 and 2, in the 
: mouth of Agua Caliente 
| } y Canyon. Station 1isin 
/ rocks on the bank of the 
wash running out of the 
canyon, immediately 
southeast of the fine 
spring of tepid water 
which gives this canyon 
its name. This is the 
- lowest Station for any 
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- 
x tomical characters are 
Fig. 5. Genitalia of S. w. aguacalientensis, Sta- 
tion 2, with detail of penis-papilla (pp.).  epi., unknown. The shells 
epiphallus; Pp.» penis; vag., vagina; v.d., vas measure 19 to 24 mm. in 
acer diameter and live in 
crevices or under fragments of a friable, shale-like rhyolite, of a dark 
vinaceous-drab color. See Pl. IX, figs. 6, 6a, 60. 
