Mammals of tJie Sonoran Region. 27 



C'ariac'us Mephiti;^ 

 Antilocapra T Felis 



Cynomys Lynx 



Sitomvs * Scapanns 



Neotoma Blarina 



Thomomys Atalapha 



T Procyon Vesperugo 



Taxidea Vespertilio 



The genera Sitomys, Mephitis, Lynx, Atalapha, Vesperugo, and 

 Vespertilio range well north in the Boreal Zone, wliere each is 

 represented b}^ a single species. In the Sonoran Zone, on the 

 other hand, these same genera reach their maximum develop- 

 ment and are represented by numerous species. 



Besides the genera above enumerated, a number of subgenera 

 belong to the Sonoran Region. Among these are Ncosciiirus and 

 Parasciuriis (subgenera of Scinnis), Xerospermophihix.j Ammosper- 

 mophihisX and Ididomys (subgenera of Spermophilus), Pitymys, 

 Pedomys and Neofiher (subgenera of Arvicola), and Chaiodipiis (a 

 subgenus of Perognathus. which is almost entitled to rank as a 

 full genus). 



The Sonoran Region may be divided l:»y temperature into 

 two principal transcontinental zones, (a) Upper Sonoran, and {h) 

 Lower Sonoran ;% and each of these in turn may be subdivided 

 into arid and hnmid, divisions. 



The gray fox, Urocyon, ranges over both Upper and Lower 

 Sonoran from Atlantic to Pacific ; and pocket gophers of the 



*The generic name Hesperomys being untenable, Allen has recently 

 substituted for it the name Vesperimm, proposed by Cones as a subgenus 

 in 1874 (Bull. Am. Mas. Nat. Hist., Ill, Xo. 2, June, 1891, pp. 291-297). 

 Vesperhnus is antedated by Sihnivjs of Fitzinger, proposed in 1807, and 

 based on Gapper's Cricetus nv/oides from Lake f^imcoe, Ontario, Canada 

 (Sitzungsber. matli. nat. Classe, K. Akad. Wiss. Wien, LVI, 1867, p. 97). 

 Gapper's Cricetus myoidcs is the common white-footed mouse of southern 

 Ontario and northern Xew York, which therefore becomes the type of 

 the genus. 



■f XerospermophUus, subgen. nov., proposed for SpermopliUus mohavensis 

 (type) and the allied species of the S- splloxonta group. 



XAmmoxpcnnophiliiJi, subgen. nov., proposed for Speniwpldlm Icucurns 

 (type) and allied species. 



'i The great Lower Sonoran Zone may be split lengthwise (in an east 

 and west direction) into two belts which have not yet been thoroughly 

 differentiated. 



