M. suprà fuscus, griseo-lavatus, subtùs albus: pedum pilis sordidè albis; caudâ corpore cum capite paulò longiore; auribus mediocribus: pilis perlongis in dorso crebrè inter cæteros commixtis.

Description.—The general tint of the upper parts of this rat, is grayish brown, (very nearly resembling that of Mus decumanus); the longest hairs, which on the hinder portion of the back are one inch and a half in length, are black; the ordinary hairs are black at the apex, there is then, on each hair, a considerable space occupied by pale yellow, and the remaining, or basal portion, is grayish white; the under fur is gray: the hairs of the chin, throat, and under parts of the body, are white, and without any gray colour at the roots: the feet are covered with dirty grayish hairs: the tail, which is slender, is very sparingly furnished with minute black hairs, both above and beneath: the ears are of moderate size, of a brownish flesh-colour, and, to the naked eye, appear to be destitute of hair. The hairs of the moustaches are most of them black at the base, and grayish at the apex.

In. Lines.
Length from nose to root of tail 7 6
of tail 7 6
of tarsus 1 4¼
of ear 0 7½
from nose to ear 1 7½

Habitat, James Island, Galapagos Archipelago, Pacific Ocean, (October.)

This species is scarcely equal in size to a full grown common black rat, (Mus Rattus), the head is rather shorter in proportion, the tarsi are smaller, and the tail is longer. In the character of the fur, and length of the hairs, it very closely resembles that species: the ears are larger than in M. decumanus, and about equal to those of M. Rattus. In having the hairs of the under parts of the body of an uniform colour, (i. e. not gray at the base,) it resembles the Mus Tectorum of Savi; but the large size of that animal, the greater length of the fur, and its colouring, all serve to distinguish it from the present species, which I may here observe, is truly an old world form, and very distinct from another species, also from the Galapagos, which is hereafter described.

“It is very common in James Island, but is not found on all the islands, if on any other in the Archipelago. Although its appearance is so like that of the common rat, yet its habits appear to be rather different: it is less carnivorous, and does not appear to be so strongly attached to the habitations of man. This island was frequented, about one hundred and fifty years since, by the vessels belonging to the Bucaniers; so that the common rat might easily have been transported here. And if a very peculiar climate, a volcanic soil, and strange food, can together produce a race, or strongly marked variety, there is every probability of such change having taken place in this case.”—D.

4. Mus (Rattus var.?) INSULARIS.

M. suprà grisescenti, colore subtùs dilutiore; tarsis purpureo-nigris: caudâ corpus cum capite æquante: auribus mediocribus: vellere molli.

Description.—No. 1. The general colour of this animal is what might be termed black, there is, however, an obscure purple-brown hue on the upper parts of the body, and the sides and under parts have a grayish tint, the hairs covering the feet above are of an uniform deep purple-brown, almost black. All the hairs of the body are gray at the base: the hairs of the moustaches are long and numerous, and of a black colour, having one or two white hairs intermixed: the ears are of moderate size, and very sparingly furnished with minute dark hairs: the tail is long and slender, and has small, scattered, bristly hairs, of a brown-black colour.

In.Lines.
Lengthfrom nose to root of tail70
of tail66
of tarsus13½
of ear07
from nose to ear16