PTEROMYS GENIBAEBIS. 
constitutes a fascicle of long slender bristles, partially concealed by the second series, 
spreading far from the head, and exhibiting a character very different from the brush- 
like appendages which constitute the bearded or pencillike auricles, in several 
species of the genus Sciurus of Linnaeus. A less perceptible tuft of long, delicate 
hair arises likewise from the anterior portion of the lobe of the ear. 
The eyes have the usual character both of those of the genus Pteromys and of 
Sciurus ; they are large and prominent. The structure of the ear of our animal 
presents several peculiarities, which distinguish it from the other Javanese species. 
The interior of this organ is large, naked, and disposed transversely near the extre- 
mity of the head ; it is divided, in the middle, by a continuation of the concha, 
which separates an extensive meatus audi tori us externus from the superior cavity. 
The lobe is short, linear-oblong, with an inflected margin, and surrounds only the 
superior portion of the ear ; opposite to the continuation of the concha, it descends 
abruptly ; and from the base of its inflected margin, arises a thick tuft of silky 
hair of a white colour. The naked interior portion is partially covered by the 
bristles of the cheeks ; and the long hairs which arise from the anterior and posterior 
portions of the lobe, have already been described as affording a peculiar character to 
our animal. 
The teeth agree, in number and disposition, precisely with those of the other 
species of Pteromys. The first grinder in the upper jaw is very minute, and closely 
applied to the second : the surfaces are generally uniform ; and being calculated for 
trituration, present a few rounded tubercles. The crown of each, individually, has 
an oblong form : they are arranged transversely, but in contact with each other, so 
as to constitute an uniform, longitudinal, triturating ridge. The front teeth in the 
upper jaw have the character which is given in the generic description of those in 
the lower jaw; the base only is remaining in our specimen. 
The proportion of the extremities to the body appears the same in all species 
of Pteromys ; but in the flying -membrane, a slight peculiarity is observed in this, 
and in other Javanese species : the length of the cartilage which supports it anteriorly, 
affords the capacity of forming a more complete expansion than in other species. 
M. Cuvier observes, that both in the Pteromys Petaurista, and the Pt. Sagitta, the 
membrane forms a very acute, salient angle behind the wrist : in the former, and in 
a new species, above mentioned, the degree of expansion which this arrangement 
affords, appears very evident: the attitude in which the Pteromys genibarbis was 
placed, in the Museum, and which has been carefully preserved in the figure by the 
artist, does not exhibit the membrane completely expanded, 
