‘ix 
264 
teeth on each side of the lower jaw. The four 
ee molars in each row are true, and bear 
jour pyramidal cusps, excepting the last tooth 
in the upper jaw, which, as in Ph. Cookii, has 
only three cusps. In the upper jaw the space 
between the functional false molars and the in- 
cisors is occupied by two simple rudimentary 
teeth, the anterior representing the canine ; but 
being relatively smaller than in Ph. Cookii, 
the crowns of the two anterior incisors are rela- 
tively larger. In the lower jaw the sloping 
alveolar surface between the functional molars 
and large procumbent incisors is occupied, ac- 
cording to M. Fr. Cuvier, by two rudimentary 
minute teeth, as represented in the figure 
(fig. 88). I have not found any trace of these 
Fig. 88. 
Petaurus Taguanoides. 
in the two skulls of Pet. Taguanoides examined 
by me. In Ph. Cookii we have seen that 
there are three minute teeth in the correspond- 
ing space ; but these differences would not be 
sufficient ground to separate generically the 
two species if they were unaccompanied by 
modifications of other parts of the body. 
In Petaurus sciureus and Petaurus flaviventer 
the dentition more nearly resembles that of 
Phalangista vulpina. In the upper jaw the 
functional molar series consists of five teeth on 
each side; the four hinder ones being, as in 
Pet. Taguanoides, true tuberculate molars, but 
diminishing more rapidly in size as they are 
placed further back in the jaw; the hinder 
tooth has three tubercles, the rest four; the 
apices seem to be naturally blunter than in Pet. 
aguanoides. 
tween the functional premolar and the 
incisors there are three teeth, of which the 
Fig. 89. 
2 
> 
Petaurus flaviventer. 
representative of the canine is relatively much 
larger than in the Pet. Taguanoides; the first 
false molar is also larger and has two roots; the 
second, which is functional in Pet. ‘laguanoides, 
is here very small. The canine is more deve- 
loped ; the first incisor is also relatively larger 
and more produced. In the lower jaw the 
functional series of grinders consists of the four 
true tuberculate molars only, of which the last 
MARSUPIALIA. 
is relatively smaller, and the first of a mo: 
triangular form than in Pet. ides. Tt 
space between the tuberculate molars and 
procumbent incisor is occupied by four smal 
teeth, of which the one immediately rior t 
the molars is large, compressed, pointed, a 
has two roots; the remaining three are rm 
mentary and have a single fang; the anter 
of these corresponds to the one regarded 
canine in the upper jaw. ’ 
Among the species exhibiting this der 
formula, viz. 
Incisors 2—3; canines =: pre 
lars s—3., molars 4—* = 40, 
3—3 4—4 
are Pet. sciureus, Pet. flaviventer, 
macrurus. 
The Pigmy Petaurist differs from the } 
ceding and larger species, in having 
hairs of the tail distichous, or oranges 2 
regular lateral series like the barbs of a fea’ 
and in having the spurious molars large: 
sharp-pointed; and the true molars bris 
each with four acute cusps. This tendene 
the dentition to the insectivorous cha 
with the modification of the tail, induced 
Desmarest to separate the Pigmy 
from the rest of the species, and const 
new sub-genus for its reception under the 
of Acrobates.* » 
To Mr. Waterhouse, however, is due 
credit of having first pointed out that the Pi, 
Petaurist had but three true molars on each 
of each jaw instead of four. There seems, t 
fore, to be better reason for accepting this s 
generic section, although we evidently peree 
a transition to this condition in the sm 
of the hinder or fourth molars in the Se 
Petaurist and its congeners. 
The description of the dentition of the Pig 
Petaurist in the Régne Animal, besides be 
defective in this remarkable particular, is” 
quite exact in other respects. In four ai 
specimens, two of which were males, and 
females with young in the pouch, I find the 
lowing dental formula to be constant (fig. § 
3— 1—1 id 
ieee a pr 
> > 
re 
ja 
Incisors canines 
lars 
The three quadricuspidate grinders of thew 
jaw are preceded by three large premol. 
of which has two fangs, and a com 
triangular sharp-pointed crown, slightly bu 
* Axpog, summus, Bawo, gradior, as frequent 
the summits of trees. . 
