frequents barns, and is thus sometimes mistaken for the Common Mouse, from which, however, it is to be distinguished by its coloration and longer ears. The latter, M. musculus, is too familiar to need much description. A curious variety of it has occurred. This has a thickened and a folded skin like that of a Rhinoceros, and the hair has disappeared. The Black Rat, M. rattus, is like a large Mouse, and is smaller and blacker in colour than the "Hanoverian Rat." It is sometimes called the "Old English Rat," but seems nevertheless to be not a truly indigenous Rodent. It has been so defeated by competition with the Hanoverian Rat that it is now not a common species in this country.
The Hanoverian or Brown Rat, M. decumanus, is a larger and a browner animal than the last. It is very widely distributed through the globe, no doubt largely on account of the fact that it is readily transported by man. The same is the case with the Common Mouse, whose real origin must be a matter of doubt. The original home of the Brown Eat is thought by Dr. Blanford to be Mongolia. There is so far a justification for the name "Hanoverian Rat" that the animal seems to have reached this country about the year 1728. But there is no reason for calling it, as is sometimes done, the Norway Rat.
Some members of this genus, whose fur is interspersed with spines, or which are quite spiny, have been separated as a genus, Leggada, which, however, is not generally allowed.
Closely allied again is Chiruromys, which has a strongly prehensile tail, a feature which is not common among the Myomorpha, though Dendromys, a tree-frequenting form, and Mus minutus, already spoken of, show the same character. Many Mice seem to have prehensile tails, which they can curl round branches; but it is not so fully developed as in the species just named.
A number of other genera are referable to the true Mice, the sub-family Murinae of Thomas's classification. The Syrian and African Acomys has very spiny fur, so much so that "when it has its spines erected it is almost indistinguishable at the first glance from a diminutive hedgehog." The genera Cricetomys, Malacomys, Lophuromys, Saccostomus, Dasymys are restricted to the Ethiopian region. Nesokia is Oriental, reaching
