66o 



COLLEGE ZOOLOGY 



with large claws suitable for digging (Fig. 523). They occur 

 in the western and southeastern states, where they burrow into 



meadows and throw 

 out mounds of 

 earth. Grain and 

 vegetables are car- 

 ried in the pouches 

 and such quantities 

 are destroyed as to 



FIG. 523- The pocket gopher, Geomys tuza. , f i ro H Pn t<; 



(From Davenport, after Bailey.) 



quite injurious. 



The family MURID.E includes the muskrats, lemmings (Fig. 

 524), meadow-mice, white-footed mice, and rats. About one- 

 fourth of our mammals belong to this family. They are all 

 small, the muskrat being one of the largest American species. 

 The common house mouse, 

 Mus musculus, the Nor- 

 way rat, Epemys norvegi- 

 cus, and black rat, E. rattus, 

 have all been introduced 

 into this country from the 

 Old World. 



The porcupines (C(EN- 

 DID^E) are characterized 

 by the presence of spines, 

 which normally lie back, 

 but can be elevated by 

 muscles in the skin. The 

 Canada porcupine, Ere- 

 thizon dorsatus, ranges 

 over northern North 

 America. 



Order Edentata. AMERICAN EDENTATES. The edentates 

 are mainly inhabitants of South America; only one species, the 

 nine-banded armadillo, reaches the southern boundary of the 



FIG. 524. The Norwegian lemming, 

 Myodes lemmus. (From Ingersoll.) 



