This species is about one-third the size of the last, it differs
moreover in being gray instead of brown, and in having the posterior
margin of the ear emarginated; the tail is also rather shorter in
proportion.
The skull[41] is figured in Plate 33, fig. 1, _a_, and 1, _b_; and fig.
23, _a_, Plate 34. Its length is 1 inch, 4½ lines; width 9¼ lines;
length of nasal bones 6 lines; distance between fore part of incisors
and the front molar (upper jaw) 5 lines; longitudinal extent of the
three molars of upper jaw 3 lines; length of auditory bullæ 5¾ lines;
length of _ramus_ of lower jaw (see Plate 33, fig. 1, _c_,), without
incisors, 11½ lines. Fig. 23, _c_, Plate 34, represents the inner side
of a _ramus_ of the lower jaw: fig. 1, _d_, Plate 33, is the lower jaw
seen from above: fig. 23, _b_, Plate 34, is the same seen from beneath.
This view is given to show the position of the descending ramus of the
lower jaw—that it springs from the outer side of the alveolar portion,
as in a great portion of the South American Rodents, such as
_Dasyprocta_, _Myopotamus_, _Echimys_, _Chinchilla_, and also in that
genus found in the West Indian islands, _Capromys_. Fig. 1, _e_, Plate
33, represents the molar teeth of the upper jaw, and fig. 1, _f_, those
of the lower.
“This species is abundant on the dry hills, partly covered with bushes,
near Valparaiso.”—D.