^9 



MONOOKAPriS OF NORTH AMERICAN RODENTIA. 



upon to prove the position we assume regarding certain nominal species, that 

 no detailed description is required in this connection. Some general observa- 

 tions, however, will not be out of jdace here. 



Tiio under parts of the ndult animal are snowy white, and this includes 

 the upi)cr surfaces of both fore and hind feet to the wrisi, and ankle, and 

 usually the greater part of the outside of the fore leg also, so that the sharp 

 line of dcmarkalion between the white and the color of the upper parts gen- 

 erally passes in a pretty straight line by the shoulder along the side of the 

 neck and side of the head, a little l)elow the eye, to the snout. But the 

 extension of color down the fore leg is utterly indefinite, for two reasons: — 

 first, in tlie young, while still gray, tiie color normally reaches the paws, and 

 its subsequent restriction is a matter of gradual change with age ; yet a great 

 many individuals do not seem to perfect this change, but remain for some 

 seasons at least in the same condition ; and, secondly, many young ones have 

 the outside of the legs as largely white fis they ever become in the old. As 

 a si)ecific character, therefore, tliis feature is not of the slightest consequence. 



In general, the color of normal adult examples, as No. 1434 from Massa- 

 chusetts, is a rich fawn, witli a pretty well defined dorsal darkening length- 

 wise from occurrence of black-ti|)ped liairs along the back. But this "typical" 

 coloration is expressed in noticeably few of the specimens that make up an 

 average miscellaneous lot — probably not one in six ; while the departures from 

 it defy description. 



This is, moreover, independent of the normal regular change of pelage 

 witli age. The young are at first i)luinbcou.x-gray above and ashy-white 

 liclow, without a trace of brown or fulvous shade ; this has to change gradu- 

 ally into the hue given in the last paragraph. In a considerable proportion of 

 .spocimcus, the change is observed to begin along the sides as an indistinct 

 stripe of fulvous ; and this progresses until the whole pelage is changed. 

 This lateral .stripe is sometimes pretty sharp, but oHener merges insensibly 

 into the gray color ; so that we are unable to lay down any appreciable stages 

 in the transition. .1 .'■ ' 



It is also liighly probable that a considerable percentage of individuals 

 pass their whole lives in a pelage nearer gray than iiiwn color; and it is 

 uu(iuestional)le that the animal can and does breed in such condition. 



In the vast majority of instances, the tail is pretty shaqdy bicolor — white 

 underneath, and on top corresponding in color to the back. The dark area 



