1915.] NATURAL SCIENCES OF PHILADELPHIA. 363 



MOLLUSCA OF THE SOUTHWESTERN STATES, VII: THE DRAGOON, MULE, 

 SANTA RITA, BABOQUIVARI, AND TUCSON RANGES, ARIZONA. 



BY HENRY A. PILSBRY AND JAMES H. FERRISS. 



This paper and the preceding one (VI) contain the account of 

 mollusks collected in course of our explorations in 1910, from the 

 middle of August to the middle of October, The forms obtained 

 in the Santa Catalina IVIountains will be described in connection 

 with the collections made there by one of us (Ferriss) in 1913. We 

 were ably assisted in the field by Mr. L. E. Daniels.^ Besides the 

 ranges enumerated in the title, some account is given of several 

 minor hill groups, all in the region south of the Southern Pacific 

 Railroad. While this paper, with those already published on the 

 Chiricahua and Huachuca Ranges, is monographic for the mollusks 

 of Arizona south of the Southern Pacific, yet the field is far from 

 exhausted. Our work is a reconnaissance rather than a complete 

 malacological survey. Further species will reward search in the 

 southwestern end and outliers of the Chiricahuas, the southern 

 Dragoons, the Whetstone Range, and the mountains around and 

 south of Tombstone. Further west we have explored only small 

 middle sections of the Santa Rita and Baboquivari Ranges. Many 

 hill and mountain groups between Tucson and Nogales remain 

 untouched, most of them doubtless inhabited by endemic species 

 of Sonorella. In the nearly waterless region westward between 

 the Baboquivari Range and the Colorado River, almost nothing 

 has been done aside from some account of the snails of the Comobabi 

 Mountains, which we are now giving. 



Going westward in southern Arizona from the eastern limit of the 

 State, the general level falls and the mountains become lower and 

 smaller. There is a gradual elimination of snails requiring a reason- 

 able degree of humidity. AsJimunella and Oreohelix extend west to 

 the Htiachucas. Beyond that range they disappear. The small 

 shells also abruptly diminish in number of genera and species, by 



' We are indebted to Mr. J. C. Blumer, of Tucson, for several species from the 

 Comobabi and Cababi Mountains, which we did not visit. 



