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 Gyvi7iobelideus, 

 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 Fetmirus; 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 

 Petaurua, but with a less develoiDment of the anterior cusjd; 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 Gymnohelideus. The 

 external muscular depression is even shallower than in Petaurus 

 hreviceps. In Gymnobelideus according to the figure the depression 

 ends in front rather sharply towards the lower part of the jaw, 

 as in Petaurus. In PaUeo petaurus 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 Gymnohelideus 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 

 Gymnohelideus. 



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 Gymnohelideus, and differ from those 

 of Petaurus in the absence of the post-orbital ridges. 



