BY R. BROOM. 569 
inner cusps very small and brought close together, giving the 
tooth more of a rounded triangular shape than the rough quad- 
rangular in Petaurus — judging from the figure a similar condition 
would seem to be present in Gymnobelideus) second molar appar- 
ently similar to the first and thus differing from Gymnobelideus, 
where it appears to be oblong and quadrangular; the fourth 
molar appears to resemble that of the two allied genera. 
Lower Jaw : — Incisor well developed, almost horizontal, sharp 
pointed and curving slightly upwards; minute premolars unknown, 
but judging from the sockets probably as in Petaurus; fourth pre- 
molar about half the size of the first molar with a blunt pointed 
cusp on the middle of the anterior half, and a rounded cusp on 
the posterior end; the first molar similar in structure to that in 
Petaurus, but with a less development of the anterior cusp; the 
second molar differs from that in Petaurus in having a greater 
development of the anterior and inner cusp, which from the inner 
side gives it much the appearance of the first molar; third and 
fourth molars unknown. 
The lower jaw is much slenderer than in Petaurus, and bears 
a considerable resemblance to that in Gymnobelideus. The 
external muscular depression is even shallower than in Petaurus 
breviceps. In Gymnobelideus according to the figure the depression 
ends in front rather sharply towards the lower part of the jaw, 
as in Petaurus. In Paiceopetaurus the depression ends, but not 
abruptly, somewhat above the line of the axis of the jaw, and 
thus differs from both the allied genera. The angle of the jaw 
appears to be slender, and more like that of Gymnobelideus than 
of Petaurus. 
Of the upper jaw little is known beyond the teeth, but sufficient 
of the palate is preserved to show that though there may have 
been a palatal vacuity, it must have been much smaller than in 
Gymnobelideus. 
I have discovered two perfect frontal bones, which, with little 
doubt, are to be referred to this form. These present a remark- 
able resemblance to those of Gymnobelideus, and differ from those 
of Petaurus in the absence of the post-orbital ridges. 
