VOL. XVII, pp. 139-146 JULY 14, 1904 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



_, : L_ 



NEW AND LITTLE KNOWN KANGAROO RATS OF 

 THE GENUS PERODIPUS. 



BY C. HART MERRIAM. 



The kangaroo rats, a group peculiar to the arid parts of North 

 America, are represented by three genera Dipodomys, Perodipus, 

 and Microdipodops. The latter is very much more distinct from 

 the others than they are from each other. Dipodomys and 

 Microdipodops have been previously studied, and the species 

 have been published, but up to the present time only a begin 

 ning has been made in working out the species of Perodipus. 

 A study of the rich collections of the Biological Survey leads 

 me to recognize nine new forms, which are here described. One 

 of these, named ingens, is a very large animal for a kangaroo 

 rat, equaling in size Dipodomys spectabilis from Arizona and 

 New Mexico. It inhabits the hot Carrizo Plain and adjacent 

 southern end of the San Joaquin Valley in California. Another 

 species, P. microps, from Lone Pine, Owens Valley, is the 

 smallest of the genus thus far discovered, being smaller even 

 than ordi and columbianus. 



A curious feature connected with the kangaroo rats of this 

 genus is that most of the species and subspecies may be arranged 

 in four groups according to size: The small ordi group, the 

 slightly larger montanus group, the decidedly larger agilis group, 



25 PROC. BIOL. Soc. WASH. VOL. XVII, 1904. (139) 



