RODENTIA. MURID^. 61 



Dimensions. 



in. t'lhs. 



Whole length, 5 1 



Tail, 15 



Observations. This species differs from the preceding in color. 

 It is far less common. I have met with only two individuals. 

 These were discovered in Williamstown, four years since. That 

 it is not an albino, is rendered probable by the color of its eyes, 

 which were black, and that it is not an accidental variety, is also 

 probable from the fact, that the two individuals belonged to the 

 same nest. The size appears to be less than the common Field 

 Mouse. 



3. Arvicola Emmonsii. De Kay. 



Specific characters. Color brown above, which extends along 

 the tail in the form of a ratiier wide line ; white beneath, includ- 

 ing the feet ; hind legs longer and more robust than the fore legs ; 

 tail a little longer than the body. 



Description. Head rather large and obtuse ; ears roundish ; 

 naked on the upper border on both sides ; tongue smooth ; in- 

 cisors without grooves ; molars tuberculated, the first in each jaw 

 the largest, diminishing in size to the last, which, when worn, 

 present a circular disc, but almost without tubercles ; four toes 

 on the fore feet, with a rudiment of a thumb, but without a nail ; 

 five on the hind feet ; nails concealed in the white hair ; hind legs 

 the longest ; tail tapering, hairy ; mystachial bristles numerous, 

 some of which are black or dark-brown for one half their length, 

 the remainder grayish or whitish ; color brown above ; darker 

 along the back than the sides ; the former color extends along the 

 upper side of the tail in the form of a stripe, and occupies about 

 one third of its circumference ; nose also brown, the upper part 

 like the back ; the brownish extends to the heel joint behind ; 

 white beneath, including also the feet, nostrils, the front and back 

 part of the fore legs, and extending along the sides to the thighs, 

 which are also white on the front and back parts, and running to 

 the extremity of the tail ; feet all white, which gives a very clean 

 and neat appearance to the animal ; line dividing the brown from 

 the white well defined ; fur bluish-black on all those parts which 

 are brown. 



