animal from the frontier of China. But a grave difficulty arises, because the feet
of this mouse do not agree with Dr. Gray’s description of the feet of Vcmdeleuria.
He says: cc Hind feet very long, slender; soles bald beneath; toes 4'5; long, slender,
compressed, the three middle subequal, the hinder middle very long; the front
outer very rudimentary, scarcely visible; the front inner weak, the hinder outer longer
than the inner; claws small.” In the mouse frQm the Nampoung and which I have
already said is identical with Elliot’s specimens, the following is a description of the
feet: hind feet rather long and somewhat expanded towards the toes; soles bald
beneath, and the pads much more strongly developed than in ground mice, and
having the form generally characteristic of arboreal rodents; toes rather long,
slender, and compressed; toes 5*5; inner toe of fore foot quite rudimentary, but with
a nail; the front outer toe rather feeble; the three middle hind toes are subequal and
rather long; the hinder outer toe is longer than the inner. The inner and outer toes
of both feet are furnished each with a small flattened nail which is so rudimentary
on the outer toe of the fore foot that it may occasionally be lost; the remaining
toes have short strong claws. Erom a comparison of this description with that of
Dr. Gray’s, it will be observed that there are important structural differences regarding
the feet which make it doubtful that the mice sent by Sir Walter Elliot and
regarded by Blyth and Jerdon as Vandeleu/ria, really belong to that genus if Dr. Gray’s
description is accurate. But it seems apparent from the internal evidence of
Dr. Gray’s description that some errors have crept into it, because the fore foot is
said to have only four toes and yet to have the three middle toes subequal.
Moreover, it will be remarkable if the front outer were the rudimentary, and not
the inner toe.
Notwithstanding the difficulties of reconciling the description of Vcmdeleuria
with Elliot’s specimens and with this mouse from the Nampoung, I am still inclined
to consider that this was the animal Dr. Gray had in view, but the doubt which I
have expressed can only be solved by a reference to the type specimens in London.
With regard to the characters of this mouse more in detail: I have mentioned the
circumstance that true claws are restricted to the 2nd, 3rd, and 4th digits, the 1st and
5th digits of each foot being provided with a flattened nail. There is also another
feature of the 1st and 5th digits, namely, the considerable development of the ungual
cushions which are full and rounded and not laterally compressed like the cushions
of the clawed digits, which are also much more prominent than in ground mice.
The pads on the soles of the feet resemble in their form and development the same
structures on the feet of that long-tailed tree and ground rat which is generally
known in India as Mus rufescens, and they are relatively much more developed than
in the pads of such thoroughly ground mice as Mus urbanus. The transverse plates
also resemble in character these plates in M. rufescens, and are very much more
perfect and like the transverse plates on the under surface of a gecko’s toes than the
broken up plated on the toes of such small ground-mice as M. urbanus. With
regard to the dentition: in the mice sent by Sir Walter Elliot, the upper incisors
present a raised line down the longitudinal mesial line of the front aspect of the
tooth, with a not very well-marked groove on either side of it, close to the sharp
line defining the lateral margins. Dr. Gray, however, describes these teeth in
Vcmdeleuria as having a deep groove near the middle on the oblique front edge.
Such another discrepancy as this between the teeth of these mice I am dealing
with and Dr. Gray’s Vcmdeleuria make me hesitate to pronounce them the same. I
have before me mice agreeing with Elliot’s specimens from the valley of the Upper
Godavery, from Berar, Allahabad, Katmandu, Nepal, Assam, Burma, and the
Kakhyen hills, and all of which have their upper incisors grooved as I have just
described them. If the molar dentition is compared with that of M. homurus,
a mouse about the same size, the characters wherein it differs from that of ordinary
mice will be brought out. In M: homurus there are transversely three cusps to
the first and second folds, while there are only two cusps to the third fold, the
inner cusp not being developed. In this long-tailed arboreal mouse the same
number of cusps exist, but the outer cusp of the third fold is not developed, or
only very feebly so. The folds are much more bent on themselves at their middle
through the mesial cusp than in M. homurus and M. urbanus. In the former
there are two folds to the second molar and three cusps to each fold, the posterior
external cusp being the least developed. In this mouse the second tooth has
two mesial cusps, one behind the other, the posterior being somewhat backwardly
elongated. External to the anterior of these cusps there are two small cusps,
and internally one large cusp tending to divide in two. External to the posterior
central cusp there is one small cusp, and at its internal border only a ledge of the
cingulum. In the last molar of M. homurus there is one small central fold, the
inner end of which tends to form a cusp, with another anterior to the latter
internally and one behind it. In these supposed examples of Vcmdeleuria there is
one fold so bent on itself that it encloses an islet in its centre, and externally
it gives off a small cusp, a part of the fold nearly constricted off, and anterior
to the hinder end of the external extremity of the fold. Behind the point where
the two ends of the fold come in contact posteriorly, there is a well developed
cusp.(unicuspulate fold).
The first fold of the first lower molar of M. homurus is divided into two cusps,
which is also the case more or less with these supposed examples of Vcmdeleuria, and
the external cusp of the third fold of Vcmdeleuria is much less developed than in
M. homurus. The other teeth differ but little. Erom this description it is evident
that the dental characters by which these forms differ from ordinary mice are not
at all well defined.
The form of the skull is much the same as in Mus, but the skull presents a
structural difference at its base, which, taken in conjunction with the grooving of
the incisors and thé absence of a true claw on the 1st and 5th digits of both feet,
would seem to entitle this form to sub-generic rank, but not to more.
The features to which I allude are the structure of the posterior nares,
pterygoid fossa, and infraorbital foramen. The former, instead of being narrow
and short, as in mice generally, are wide and long, and on looking into them from