When at Paris I examined what I believe to be the original Mus Braziliensis, since the specimen was labelled “Rat de Brazil St. Hilaire, 1818.” It agrees perfectly with the present animal excepting in being rather smaller, the length from the nose to the tail being 7 inches and 4 lines—the length of the tail is 7 inches 9 lines, and that of the tarsus is 1 inch 11 lines; this difference in the length of the body may arise from difference of age, or even of sex. In the Paris Museum I saw what appeared to me to be a variety of the same species in which the under parts of the body are white.

I have been minute in my description of the Mus Braziliensis, since it is confounded by Desmarest, Fischer and Lesson with the Rat troisieme or Rat Angouya of Azara, which I believe to be a very different animal. The description given by the authors just mentioned are taken from Azara, who gives the following characters to distinguish the Rat Angouya: “Du museau à la queue, et sur les côtés du corps tout est brun-cannelle, parceque les poils ont une petite pointe cannelle; puis, ils sont obscurs et enfin blanc vers las peau. Toute la partie inférieure de l’animal est blanchâtre, plus claire sous la tête, et plus foncée entre les jambes de devant; le pelage est doux, très-serr, et le poil, qui est à la racine de l’oreille, cache le conduit de celle-ci.”

In. Lines.
Length from nose to root of tail (English measure) 6 0
of tail 6 6½
of ears 0 9¾
of tarsus (the claws included) 1 3¼

It appears from this description that the Mus Angouya is a smaller animal, and differs both in colouring and proportions from the Mus Braziliensis. Brandt has figured and described a rat under the name of Mus Angouya, which in many respects agrees better with Azara’s description; there are, however, discrepancies in the dimensions.

22. Mus micropus.
Plate XX.

Mus micropus, Waterh., Proceedings of the Zoological Society of London for February 1837, p. 17.

M. suprà fuscus; subtùs cinerescenti-albus, pallidè flavo tinctus; pedibus pilis sordidè albis tectis, antipedibus parvulis; auribus parvulis; caudâ, quoad longitudinem, corpus ferè æquante, suprâ fuscâ, subtùs sordidè albâ.

Description.—Form stout, ears rather small, tail nearly equal to the body in length, fur very long and moderately soft, general colour of the upper parts of head and body, brown; of the sides of the body grayish, faintly washed with yellow, of the under parts grayish white, faintly tinted with yellow; hair covering the upper surface of the feet dirty white; on the tarsus there is a very slight yellow tint; ears well clothed with hairs, those on the inner side chiefly of a yellow colour; tail above, dusky brown; beneath dirty white: hairs of moustaches black at the base and grayish at the apex; incisors pale yellow: hairs of the back deep gray at the base, annulated with brownish yellow near the apex, and dusky at the apex; longer hairs dusky black; hairs of the belly deep gray at the base and broadly tipped with yellowish white.

In.Lines.
Lengthfrom nose to root of tail60
of tail38
from nose to ear14
of tarsus (claws included)10¾
of ear06

Habitat, Santa Cruz, Patagonia, (April.)