THE MOUSE TRIBE. 127 



stores for winter use. These stores are generally accumulated in hollow trees or 

 logs, and sometimes may contain two or three quarts of beech-nuts or clover-seed. 

 This mouse, unlike the hamster, remains, however, active throughout the winter; 

 and may be seen running about on the snow, where its long tail leaves a character- 

 istic track. It is an agile climber, running up tree-stems with the activity of a 

 squirrel, and frequently disappearing in some hole at a great distance above the 

 ground. In addition to nuts and seeds, the white-footed mouse will readily eat 

 the flesh of such animals as come in its way, and it is possible that it may occasion- 

 ally kill small birds for itself. From three to six young are produced at a birth, 

 and there appear to be several litters during the year. The first coat of the young 

 is of a uniform dull grey colour. In the northern portions of the range of this 

 mouse, the nest is generally built either in the hollow of a tree or a log, or in a 

 burrow: but more to the south these animals construct an "outside nest" of moss, 

 grass, leaves, or bark, which is generally more or less cocoanut-shaped, and may be 

 as much as a foot in diameter. It is usually suspended from a horizontal branch 

 at some' distance from the ground, and has its entrance on the under surface. The 

 group to which this particular species of white-footed mice belongs is distinguished 

 by having only five tubercles on the first molar tooth in the upper jaw. The rice- 

 tield mouse ((.'. falustris), which attains the size of a small rat. does much damage 

 to the rice crops in the Southern States. 



The Fish-Eating Rat. 



( ienus Ichtkyomys. 



A remarkable species ( /. Miilinm n ni) inhabiting the mountain -streams of 

 central Peru is allied to the preceding group, but distinguished by its aquatic and 

 probably fish-eating habits, as well as by its webbed and fringed hind feet. In 

 size it comes near the brown rat, but has the head much flattened, larger whiskers, 

 and very small ears and eyes: while in colour it is dark above and whitish 

 beneath, with a black-and-white tail. 



The Gkooved-Toothed Mice. 

 Genera Rhithrodontomys and Rkithrodon. 



Two groups of American Cricetines are distinguished by their upper incisor 

 teeth being marked by parallel grooves. Of these, the American harvest-mouse 

 [Rkitkrodontomys hv/mUis) resembles the rice-field mouse in external appearance, 

 and is found in the southern United States as far north as Iowa ; the two other 

 species of the genus being also North American. 



The Rhithrodonts, on the other hand, are exclusively South American, and 

 are characterised by their rabbit-like appearance, the head being very short, with 

 a highly convex profile, very large eyes, and rather large rounded ears. The 

 rabbit-like rhithrodon (Rkithrodon cuniculoides), from Patagonia, is one of the 

 best known species. The length of the head and body is Gi inches, and that of 



