338 
ACK0BATA. 
developed premolars, which are compressed and pointed, and 
present nearly a triangular outline when viewed on the outer 
or inner side, hut each of these teetli has a very small anterior 
and posterior cusp at the base ; they are all two-rooted, and 
the middle tooth is a trifle larger than the others, which are 
about equal in size ; the hindermost premolar is in contact 
with the true molars, the remaining two are separated from 
each other, or from the canine, or the last premolar, by 
narrow interspaces : the three true molars are small, and suc¬ 
cessively decrease in size from the first to the last; the 
two foremost have two outer, pointed cusps, and two smaller 
inner cusps ; the last molar has but three cusps. The two 
incisors of the lower jaw are very long, pointed, and nearly 
horizontal, and are followed on either side by two small, 
simple premolars ; then two other well developed premolars, 
having the crown much elevated and pointed (the foremost 
most so), and a small posterior cusp; they are two-rooted. 
The three true molars have each four cusps ; the outer anterior 
cusp of the first of these teeth is most elevated. All these 
teeth of the lower jaw form an uninterrupted series. 
This dentition, it will he perceived, agrees very closely with 
that found in Dromicia, the chief difference consisting in the 
greater development of the premolars in Acrobat a. In both 
cases there is an approach to the insectivorous type of deuti* 
tion (most marked in Acrobat a ), as evinced in the small 
size of the true molars, when compared with those of the 
large Phalangers, and the greater importance which the pre¬ 
molars assume : the peculiar triangular form, and the 
presence of two roots, in many of these teeth, remind us 
strongly of the premolurs in the small insectivorous Marsu¬ 
pials, such as the Phascogales 1 . 
1 I cannot help here calling attention to certain points which I have endea¬ 
voured to illustrate elsewhere, viz. that the affinities of species of one group 
to species of another, are more near, or more remote, according to the rank of 
