MAMMALS OF THE MEXICAN BOUNDARY. 



463 



paler, dusty, grayish color and in having more hairy tails, the hairs 

 concealing the caudal annuli. Those from the Colorado River are 

 almost as pale, but have a more yellowish coloring. An extreme 

 specimen (Cat. No. 60157, U.S.N.jM.), from the Colorado at Monu- 

 ment No. 204, is of a yellowish rust-color, almost exactly intermediate 

 in coloration between the type of R. megalotis deserti and a specimen 

 of the R. mexicanus group from Alazatlan, Mexico, and suggests an 

 afiinity between the R. mexicanus and R. megalotis groups. 



Ilahits and local distribution. — In March, 1894, we found the desert 

 harvest-mouse abundant along the Colorado River from Yuma to the 

 Gulf of California. Its favorite home was amongst the dense growth 

 of arrowwood that covers so large an extent of the Colorado bottom 

 lands. On the Colorado Desert a few were taken at Seven Wells and 

 Gardners Laguna, on the Salton River, in Ijower California, in April, 

 1894. Females taken April 15 and 20, 1894, would have given birth 

 to 4 young each. 



Record and measuroneiits of 39 specimens of Reithrodontomys megalotis deserti. 



