34 
ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 
This rat is very closely allied to Mus decumanus, and I think may possibly 
prove an extraordinary local variety of that animal. Having but one skin, and no 
skull, I am unable to satisfy myself on this point. Its size, as will be seen by 
the admeasurements, exceeds that of the common rat, or, rather, it exceeds 
ordinary specimens of that animal, for I have seen some which were equal 
to it. 
“ It. was killed near Maldonado, where it frequented holes in the sand 
hillocks near the shore. It is likewise found on the island of Guritti. If ships 
are ever infested with these monstrous rats, the above-mentioned localities 
are very likely places to have received colonies by such means. An old 
male weighed fifteen ounces and three quarters. The ears of this rat, when 
alive, were of a pale colour, which made a singular contrast with the black fur 
of its body.” — D. 
3. Mus Jacobue. 
Mus decumano'ides,* Waterh. in “ Catalogue of the Mammalia preserved in the Museum of the Zoological 
Society of London.” 
M. supra fuscus, griseo-lavatus, subtus albus : pedum pilis sordide albis ; caudd cor- 
pore cum capite pauld longiore; auribus mediocribus: pilis perlongis in dor so crebrs 
inter cceteros 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. 
* The MS. name of M. decumano'ides , which I had applied to this animal, has been changed, in conse- 
quence of my having seen a different species, with the same name attached, in the museum of the India 
House. 
