.in-; MONOGRAPHS OF NORTH AMERICAN RODBNTIA. 



dress is worn for only about lour months, the vernal change beginning in 

 March; in the middle districts, aboul five months, and in the higher latitudes 

 about six, where the winter dress, according to Dr Richardson, is worn till 

 the end of April. 



Summer specimens of var. virginianus from Massachusetts, New York, 

 and Pennsylvania vary considerably in color through the varying intensity 

 of the brown tints of the upper surface and the relative length of the black 

 tips of the hairs. In some, the black tips are short and inconspicuous; in 

 others, so long as to strongly vary the general color with black. The brown 

 varies from pale yellowish-brown to dark reddish-brown, the brown tint of 

 the under fur also similarly varying in intensity. The base of the under-fur 

 varies from grayish to dark plumbeous. 



The exact ranges of varieties americanus and virginianus cannot now be 

 well determined, and, as in the case of other intergrading geographical forms, 

 cau probably never be absolutely defined. According to Dr. Gilpin, the 

 Nova Scotia type seems clearly referable to the northern form (var. ameri- 

 canus). He describes the dorsal surface as being "sepia-brown, with a yellow 

 wash", and observes that they present none of the bright reddish or cinna- 

 mon-brown mentioned by Professor Baird as characterizing more southern 

 specimens. Dr. Gilpin's description hence corresponds very nearly with 

 specimens from the Red River district, and from Fort Rae, Great Slave Lake, 

 and hence with Dr. Richardson's description. 



In Table XVII, the first fourteen specimens, all from Massachusetts 

 (Coll. M. C. Z.), and all in winter pelage, vary in length of body from 14 to 

 20 inches; in length of hind foot, from 4.65 to 5.50; in length of ear, from 

 2.40 to 3.60: the average being, length, 17.3?; hind foot, 5.24; ear, 2.83. 

 Fifteen other specimens (Coll. S. I.),* seven of which are also from Massa- 

 chusetts, and the others from Xew York and Pennsylvania, range in length 

 from 16 to 21 inches; hind foot, 4.57 to 5. 68 ; ear, 3.00 to 3.60: averaging, 

 length, 18.82; hind foot, 5.24; ear, 3.32. In length, the latter series exceeds 

 the former by about one and a half inches, while the hind feet are equal ; 

 the difference in the length of the ear is nearly half an inch, one-half of 

 which, at least, is due to the different way in which the measurements of the 

 ear in the two series were taken, as shown by a remeasurement of some 

 of the specimens of the latter series. 



In Table XVIII are presented the measurements of twenty-three 

 ' Measurements copied from Baird'a Mamm. N. Am. 



