nearly-allied, but smaller species, the BUSHY-TAILED WOOD RAT (_N. cinerea_), inhabits the western and north-western parts of America, also extending eastward to Hudson’s Bay, and southward to New Mexico and California. The COTTON RAT (_Sigmodon hispidus_), another inhabitant of the Southern States and Mexico, ranges southwards to Vera Cruz and Guatemala. Besides several species of _Hesperomys_, South America possesses various Murine animals, which have been placed in special genera. Among these the most remarkable are those of which Mr. Waterhouse formed his genus _Reithrodon_, as these, although true Murines, have a very Rabbit-like character, and further present the peculiarity of having the upper incisors grooved. They have the profile much arched, the eyes large, the ears hairy, and the first and fifth toes of the hind feet very short. The tail is well clothed with hair. The RABBIT-LIKE REITHRODON (_R. cuniculoides_) inhabits Patagonia, where it was discovered by Mr. Darwin. It is of a yellowish-grey colour, mixed with black, with the throat and belly pale yellow, and the rump and feet white. The tail is about half the length of the head and body, dusky above, white beneath. The length of the head and body is six inches and a half. Two other species are described: one (_R. typicus_) from the La Plata; the other (_R. chinchilloides_) from the Strait of Magellan. [Illustration: HEAD OF THE RABBIT-LIKE REITHRODON.] The HAMSTERS, forming the sub-family CRICETINÆ, are very nearly related to the true Mice and Rats, but differ from them at the first glance by their possession of large internal cheek-pouches, those organs being entirely wanting or very small in the Murinæ. Their molars, three in number in each series, are also tuberculate when young and regularly rooted. As age advances they become more and more worn away, so as to exhibit folds of enamel. They are stoutly-built rat-like animals, generally with short tails, with the upper lip cleft, and with short limbs, of which the hinder have five, and the anterior four, toes, the thumb being represented by a small wart. The Hamsters are confined to the Old World, and chiefly inhabit the temperate parts of Europe and Asia; two or three species occur in Africa. They live generally in corn-fields, where they dig deep burrows with numerous chambers, into which they can retreat to take their repose, and in which they pass the winter, previously, however, taking care to lay up a good store of provisions in some of the chambers of their domicile. [Illustration: HAMSTERS.]