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In the structure of the skull Azomalurus differs considerably from 
the known species of Sciuride. All the species of the family, the 
skulls of which I have had an opportunity of examining (and they 
are numerous, embracing all the known genera and subgenera), are 
distinguishable by the possession of a distinct post-orbital process 
to the cranium; they have the palate broad, and terminating in a 
line with the posterior molars, or behind that line; the molars of 
opposite sides of the jaw are parallel, and the ant-orbital opening is 
small, in the form of a tube, and serves only for the transmission of 
the infra-orbital nerve. These characters are not found in Anoma- 
lurus ; the post-orbital process is here reduced to a mere rudiment, 
being represented by an indistinct projection forming an obtuse 
angle: the ant-orbital opening is large, and evidently affords a pas- 
sage for a portion of the masseter muscle as well as the nerve; it 
moreover opens directly in the bony plate which constitutes the an- 
terior root of the zygomatic arch, and is not produced as it were into 
a tube, as in the typical Squirrels. The palate is narrow, and has a 
deep triangular emargination behind, the apex of the triangle being 
on a line with the hinder margin of the penultimate molar. The 
molar teeth converge in front, so that the space between the two 
foremost is scarcely equal in width to one of these teeth ; the crowns 
of the molars of opposite sides of the upper jaw, instead of being on 
the same plane, or very nearly so, are directed obliquely outwards ; 
and the masticating surface of those of the lower jaw, to meet them, 
incline in an opposite direction. The incisive foramina are longer 
than is usual in the Sciuride, and encroach in a slight degree upon 
the maxillary bones. The nasal portion of the skull is narrower, and 
the nasal bones are remarkable for a deep emargination in front. 
I have been led to institute a comparison between the present 
animal and the species of the Sciuride, on account of certain points 
of resemblance which there exist between it and the Flying Squir- 
rels (Pteromys), especially in the possession of the expanded flank 
and interfemoral membranes. In the almost total absence of post- 
orbital process, however, and in the comparatively large size of the 
ant-orbital opening, the Anomalurus evinces an approach to the 
Myoxide; the approximation is moreover observable in the narrow- 
ness of the nasal bones and the slenderness of the zygomatic arch, 
these parts being compared with those corresponding in the squirrel 
skull. 
The lower jaw is formed like that of the Squirrels, and does not 
present certain peculiarities observable in the Myovus, viz. that of 
having the descending ramus perforated, its posterior angle acute, 
and the upper posterior angle produced. 
The incisor teeth are deeper than broad, and almost flat in front. 
The molars are permanently, it would appear, = for in a skull of 
a young animal in which but three molars on either side of the jaw 
are protruded, there is no trace of the small anterior molar so com- 
monly found in the Squirrels. They are very nearly equal in size, 
and of a quadrate form; the crown of each molar of the upper jaw 
