SECRETARY'S REPORT. 185 



A. Bretoeri, (Baird.)— Gray Mouse. 

 This species is said to be abundant on the Island of Muskeeget, on 

 the eastern coast of Massachusetts, where, Prof. Baird says, the only 

 specimens he has seen were collected by Dr. Brewer. 



Description. — Size large ; feet very broad and stout; soles with six 

 tubercles ; fur coarse ; ears small ; above, pale grayish-yellow ; brown 

 beneath, with the under surface of the tail, and the upper surfaces of the 

 feet strongly hoary or ashy-white, with a tinge of yellow. 

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DIMENSIONS. 



Length of head 1.31 inch. 

 Length of head and body, 4.30 inches. 

 Length of tail to end of vertebrce, 1.65 inch. 

 Length of tail to end of hairs, 1.94 inch. 

 Length of hind-foot, .85 of an inch. 

 Length of fore-foot, .41 of an inch. 



A. rufidorsum, (Baird.) 



This species is very rarely found, if it is a species existing with us. 

 Prof. Baird says, the only specimen he has ever seen was obtained at 

 Holmes' Hole, Massachusetts, and belongs to the Boston Society of 

 Natural History. 



Description. — Size large ; above, bright rufous, or reddish-chestnut ; 

 this tint paling insensibly to the belly, where it changes rather abruptly 

 to reddish- white ; no dorsal band ; feet reddish ; imder surface of tail 

 whitish. 



DIMENSIONS. 



Length of head and body, 4.20 inches. 

 Length of tail to end of vertebrae, 1.55 inches. 

 Length of tail to end of hairs, 1.85 inches. 

 Length of hind-foot, .82 of an inch- 



Genus: Fiber. — (Cuvier.) 



Characteristics. — Incisors, two in each jaw ; molars, six in each Jaw, 

 with zig-zag lamina; ; body large ; limbs short ; hind-feet partly webbed ; 

 toes with strong, somewhat curved claws ; tail long, compressed laterally ; 

 with anal glands, secreting a liquid with a strong musky odor. 



This genus is composed of a single species, the Musk Rat. It is con- 

 fined to this continent, where it is extensively and generally distributed. 



Fiber Zibeihictis, (Cuvier.) — Musk Rat. 

 The habits of this common species are too well known to need 

 particular mention here. It is almost entirely aquatic, seldom venturing 

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