402 PROCEEDINGS OF THE ACADEMY OF [June, 
Tumamoc Hill, near Tucson, Pima Co., Arizona. Types No. 
112,245, A. N. S. P., collected by Ferriss, Pilsbry and Daniels, 
October 1, 1910; topotypes in collections of Ferriss and Daniels. 
Specimens were taken by Mr. J. C. Blumer under volcanic cliffs 
on the northeast side of Cat Mountain, in the Tucson Range. 
The shell closely resembles S. eremita of the Mineral Hill group, 
but it is much thinner with the peristome decidedly less expanded 
and the embryonic whorls smoother. The penis is very much ~ 
longer than in eremita. A comparison with the unique type of 
S. arizonensis Dall, kindly made by Dr. Paul Bartsch, shows that 
that species is quite distinct. 
We would be disposed to consider twmamocensis a subspecies of 
S. rowelli were it not that in individuals having the shell about the 
same size as rowelli the penis, penis-papilla, epiphallus and vagina 
are about twice as long; the spermathecal duct remaining about 
equal in the two species. The shape of the penis-papilla is different, 
that of twmamocensis being longer, slender and tapering. For 
comparison we have added measurements of the organs of S. rowelli 
to the table on p. 408. The columellar lip dilates much less than in 
S. comobabiensis or S. sitiens. 
The penis is very much longer, its papilla both absolutely and 
relatively much shorter than in S. papagorum. 
The Tumamoc Hills are an outlying spur of the Tucson Range, 
about a mile from Tucson west of the Santa Cruz River. There are 
three hills: Tumamoc, 3,092 feet, on the northern slope of which 
the Desert Botanical Laboratory of the Carnegie Institution of 
Washington stands; Sentinel, 2,885 feet, and a lower nameless hill 
of 2,672 feet elevation. The hills are voleanic, formed of an old 
andesite flow, largely covered by rhyolite (which is the characteristic 
rock of the Tucson Range) and later flows of basalt.7 Sonorella 
occurred in great piles of black basalt, on the north slope of Tumamoce 
Hill, from just below the flat summit down half way to the Desert 
Laboratory. Most of them were taken not far from the 2,750-foot 
contour (our Station 35). Living snails are very scarce and hard 
to get. None were found on the other slopes of Tumamoc Hill, 
nor could we find them on Sentinel Hill. On the 2,672-foot hill, 
at the end of Congress St., we took only Bifidaria tuba. 
7 Topographic and geological maps of these hills, with accounts of their physical 
features and vegetation, may be found in the following publications of the Carnegie 
Institution of Washington: D. T. Macdougal: Botanical features of North 
American deserts, 1908. Volney M. Spalding: Distribution and movements of 
desert plants, 1909. z 
- Le feed el th, etith Beei aaa. 
