40 Field Museum of Natural History — Zoology, Vol. XI. 



but the limits of the latter are not so clearly marked as in the former, 

 inasmuch as animals have the power of moving about at will and 

 with few exceptions are not confined to one locality throughout 

 the year. The ranges of many species of mammals are often not 

 restricted to one zone, but may include a portion of two or more. 



It is important that the student should become familiar with 

 the location of these zones, as reference to them is often made by 

 writers in describing the distribution of species.* 



* To students, who desire to pursue this important subject further, the following 

 publications are recommended : 



Wallace, A. R. Geographical Distribution of Animals, I and II, New York, 1876. 

 Allen, J. A. Geographical Distribution of the Mammalia. Bull. U. S. Geol. 



and Geogr. Surv. Terr., IV, No. 2, 1878, pp. 313-377. 

 Allen, J. A. Geographical Distribution of N. Amer. Mammals. Bull. Amer. 



Mus. Nat. Hist., IV, 1892, pp. 199-243. 

 Merriam, C. H. Geographical Distribution of Life in N. Amer. Proc. Biol. Soc. 



Wash., VII, 1892, pp. 1-64. 

 Merriam, C. H. Life Zones and Crop Zones of the U. vS. U. S. Dept. Agric, 



Div. Biol. Surv., Bull. No. 10, 1898. 



