20 University of California Publications in Zoology Vou. 17 
ground squirrel is a comparatively recent immigrant into the lowlands 
of the San Joaquin Valley, and that it is continually increasing in 
numbers. Possibly the immigration of Citellus beecheyi tends to 
assist in the crowding out of Ammospermophilus nelsoni and the 
consequent restriction of the range of the latter. Much more evidence, 
however, must be gathered before any degree of probability can be 
assumed for the suggestions here made. 
Transmitted April 21, 1916. 
LITERATURE CITED 
MEARNS, E. A. 
1907. Mammals of the Mexican Boundary of the United States. U. 8S. 
Nat. Mus. Bull. 56, Part 1, pp. xv +530, pls. 13, 126 figs. in text. 
MerrIAM, C. H. 
1893. Descriptions of eight new ground squirrels of the genera Spermo- 
philus and Tamias from California, Texas, and Mexico. Proce. Biol. 
Soe. Wash., 8, pp. 129-138. 
PatmeEr, T. S. 
1893. List of localities visited by the Death Valley expedition. U. 8. 
Dept. Agric., Div. Ornith. and Mamm., N. Amer. Fauna, 7, pp. 
361-384. 
