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- 

 field mouse (C. palustris), which attains the size of a small rat, does much damage 

 to the rice crops in the Southern States. 



THE FISH-EATING RAT. 

 Genus Ichthyomys. 



A remarkable species (/. stolzmanni) 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-w T hite tail. 



THE GROOVED-TOOTHED MICE. 

 Genera JRhithrodontomys 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 

 (Ehithrodontomys humilis) 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 (Rhithrodon cuniculoides), from Patagonia, is one of the 

 best known species. The length of the head and body is 6J- inches, and that of 



