1906.] NATURAL SCIENCES OF PHILADELPHIA. 122 
MOLLUSCA OF THE SOUTHWESTERN STATES. II. 
BY H. A. PILSBRY AND J. H. FERRISS. 
The present paper deals with mollusks of Texas, New Mexico and 
Arizona, collected chiefly by the authors in 1903, and not included in 
the first paper of this series.1 No attempt has been made to present 
complete faunas; but in connection with the previous paper, about all 
the reliable data extant upon the snail faunas of the Chiricahua and 
Huachuca ranges in southeast Arizona and the eastern and southern 
borders of the Lower Sonoran area in Texas will be found herein. 
It has not been thought expedient to repeat data elsewhere accessible. 
For the student of molluscan distribution, the life zones of the United 
States as mapped by Dr. Merriam * emphasize the secondary and not 
the primary facts of distribution. The laws of temperature control, 
which he has developed with keen insight, do not define transcon- 
tinental zones of primary import zoologically. These zones are sec- 
ondary divisions of vertical life areas of which the molluscan faunas 
were evolved in large part independently. The Sonoran fauna is 
probably intermingling more now with that of eastern North America 
than at any former time, at least so far as such sedentary forms as 
land mollusks are concerned. 
Similar conclusions have been reached by Mr. A. E. Brown in deal- 
ing with Texan reptiles.* The results of his study ‘‘establish three 
facts, hitherto not wholly free from uncertainty: first, that the bound- 
ary between the Austroriparian and Sonoran reptilian faunas lies ap- 
proximately between the 96th and 98th meridians of longitude in 
Texas; second, that the restricted Texan district of Cope is not Aus- 
troriparian but Sonoran; third, that transcontinental zones of distribu- 
tion cannot be maintained in the Medicolumbian region for reptiles.’ 
1 Proc. A. N.S. Phila., 1905, p. 211. 
* Some New Mexican records, chiefly from material collected by Prof. T. D. A. 
Cockerell in the upper Pecos valley, are added. 
’ Biological Survey, U. S. Dept. of Agriculture, Bulletin No. 11, Map. North 
American Fauna, No. 25, Plate I. 
‘Texas Reptiles and their Fafinal Relations, Proc. A. N. S. Phila., 1903, pp. 
543-558. 
Post-Glacial Nearctic Centers of Dispersal for Reptiles, Proc. A. N. S. Phila, 
1904, p. 464. 
