218 
MACROPODID.K. 
the Bettongia section which have come under my observa¬ 
tion ; tlie zygomatic arches are less boldly thrown outwards 
than usual, and have the middle portion of the zygoma 
nearly straight; the face is somewhat elongated, and acutely 
pointed; the nasal bones narrow; the auditory bull© large; 
the palate deeply emarginated posteriorly ; the incisor teetli 
are much compressed; the canine moderate as to size; the 
premolar short from front to back, as compared with other 
species, and deeply sulcated in the vertical direction, both 
internally and externally; the number of grooves on either 
side is about seven. The foremost molar of each series is 
the largest, and the hindermost the smallest, and is about 
equal in width to two-thirds of that of the foremost molar; 
the upper outline of the skull, as viewed from the side, pre¬ 
sents a gentle and nearly even convex curve, but descends 
somewhat suddenly towards the occipital crest, and the 
interorbital space is nearly flat. 
Although there ore some slight variations in the width of 
the nasal hones, and even in the antero-posterior extent of 
the premolar tooth, it does not appear that these are con¬ 
nected with differences in the auimals, nor that such differ¬ 
ences distinguish the II. Ogilbyi from the II. penicillatus. 
A great portion of the Marsupialia possess a prehensile 
power in the tail, and in the tree-climbing Opossums and 
Phalangers this organ is used as a fifth hand, hanging by 
its means, as they do, from the brandies of trees. Iu the 
great Kangaroos, the tail, though not prehensile, still assists 
in locomotion This, however, does not appear to bo the 
ease in the Kangaroo-rats. In Hypaiprymnus minor , and 
some nearly allied species, in which the tail resembles that of 
a rat, being sparingly clothed throughout with short hairs, 
that organ appears neither to have any prehensile power nor 
to be used to support part of the weight of the body, as in 
the Kangaroos; but in the BeLLongios,—iu which the apical 
