Rat, &c.), probably in its original sense the designation of the British rodent mammal commonly known as the black rat (Mus rattus), but also applied indifferently to the brown or Norway rat (M.
Rattus) is distinguishable from the brown rat by its smaller size, longer ears and tail, and glossy black colour.
Rattus alexandrines is common in many places to which the brown species has not yet penetrated, for instance in South America.
Rattus ater) made its appearance in England.
Millais, "The True Position of Mus rattus and its Allies," Zoologist, June 1905.
It is unnecessary here to dwell upon the worldwide distribution of the two rats Mus rattus and M.