THE FIELD MOUSE. 693 



one of the quickness and ease with which some species of ducks and 

 grebes dive when shot at. 



" At the distance of ten or twenty yards, the Musk Rat comes to the 

 surface again, and perhaps joins its companions in their sports ; at the 

 same time others are feeding on the grassy banks, dragging off the roots 

 of various kinds of plants, or digging underneath the edge of the bank. 

 These animals seem to form a little community of social, playful crea- 

 tures, who only require to be unmolested in order to be happy." 



GENUS HESPEROMYS. 



This genus, with its ninety species, replaces on the American conti- 

 nent the genus Mus,. 



The New Jersey Field Mouse, Hcspcromys campestris, measures a 

 little more than three inches in length. The fur is a leaden black, the 

 head is large, the ears large, oval, blunt, and thinly covered with closely 

 adpressed hair. The legs and feet are brown. The tail well covered 

 with long hair. 



The SoNORA Field Mouse, Hcspcromys So/wricnsis, is slightly larger 

 than the New Jersey species. The hair is slate color, mixed with brown- 

 ish-gray ; beneath, whitish, except on the throat. The head is elongated, 

 the ears large, oval, and hairy. The feet are covered with short, whitish- 

 brown hair. The tail of moderate length. 



The Texan Field Mouse, Hcspcromys Tcxaiia, is smaller than the 

 above described species, only measuring two inches in length. The 

 head is large and blunt, the eyes prominent and dark-brown ; ears large, 

 erect, roundish, oval, blunt, sparsely covered outwardly with short, close- 

 lying brown hairs, inwardly with gray. The hind-feet are furred, with 

 the exception of the sole. The whiskers are long. The fur has rather a 

 mottled appearance ; beneath white, inclining to yellowish. The two 

 colors are distinctly separated in a straight line. The feet are white, the 

 hairs projecting over the nails. Its habitat is Western Texas. 



GENUS ARVICOLA. 



The fifty species of Arvicola are distributed over Europe, Northern 

 Asia, and temperate North America. 



The Water Rat, Arvicola ampliibius (Plate LIII), is found from the 

 Atlantic to the Sea of Ochotsk, and from the White to the Mediter- 

 ranean Sea, in plains, as well as in mountains. 



