1906.1 NATURAL SCIENCES OF PHILADELPHIA. 123 



MOLLITSCA OF THE SOUTHWESTERN STATES. II. 

 BY H. A. PILSBRY AND J. H. FERRISS. 



The present paper deals with molliisks of Texas, New Mexico and 

 Arizona, collected chiefly by the authors in 1903, and not included in 

 the first paper of this series.^ 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 temperatui'e 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 imcertainty : 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. 

 Cockerel! in tlie 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 Faunal 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. 



