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, Pilsbrj^ 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 closeh" 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 bj^ Dr. Paul Bartsch, shows that 

 that species is quite distinct. 



We would be disposed to consider tumamocensis 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 tumamocensis 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 verj- much longer, its papilla both absolute^ 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 volcanic, formed of an old 

 andesite flow, largely covered by rhyolite (which is the characteristic 

 rock of the Tucson Range) and later flows of basalt.^ Sonorella 

 occurred in great piles of black basalt, on the north slope of Tumamoc 

 Hill, from just below the fiat 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 ^,672-foot hill, 

 at the end of Congress St., we took only Bifidaria tuba. 



'' 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. 



