THE MAMMALS OF NEW JERSEY. 65 



usually small animals, generally nocturnal, or living in subter- 

 ranean runways so that they are seldom seen, although they fre- 

 quently do an immense amount of damage to crops. They are the 

 natural food of hawks and owls as well as of weasels and other 

 predatory mammals. 



The popular terms rat and mouse do not denote natural sub- 

 divisions of the family but are simply indicative of size, all the 

 larger species, no matter to what genus they belong, being termed 

 rats, and the smaller species mice. Our native species fall into 

 two sub-families, but like the genera they are separated by char- 

 acters which are more or less obscure and not by very obvious ex- 

 ternal differences. However, we can formulate certain differ- 

 ences which hold pretty well for our New Jersey species. Besides 

 these two groups we have several species of the true Miirince of 

 Europe, which have accompanied man wherever he has spread his 

 civilization. 



a. Thick set, short legged, short eared, short tailed ; tail less than one-third 

 the length of head and body (except the Muskrat). Mainly burrowers 



microtinjE (Meadow Mice, Lemmings and Muskrats) 

 aa. Slender, with longer legs, larger ears and eyes, and long tail more than 

 half the length of head and body, generally much more. 



CRiCETiN^ (American Long-tailed Mice and Rats) 



aaa. Similar to the last but with different skull and teeth, all natives of the 



Old World. MURINE (Introduced Mice and Rats) 



Sub=Faniily MICROTIN^. 



Meadow Mice, Lemmings and Muskrats. 



The animals of this group are arranged in several genera which 

 may be distinguished as follows : 



a. Tail long and narrow, flattened vertically, nearly naked ; animal large, 

 rat-like; total length, 24 inches. fiBEF (Muskrat) 



■aa. Tail very short, slender and hairy; animals small, mouse-like, 



b. Upper incisors with a groove (nearer one side than the other). 



SYNAPTOMYS (Lemming Mouse) 

 bb. Upper incisors not grooved. 



c. Molar teeth divided at the base into roots, ears slightly visible 

 above the fur. Evotomys (Red-backed Mouse.) 



cc. Molar teeth not divided into roots ; ears not visible above the fur. 



MiCROTus (Meadow Mice) 

 5 MU 



