684 MR. F. G. PARSONS ON THE [June 16, 
The Osseous System. 
Owen, in his ‘Comparative Anatomy of Vertebrates, has given 
an excellent account of the Kangaroo’s bones, and I only intend to 
draw attention to certain points which seem to me of special 
interest. In the first place, the chief characteristics in which the 
skull of Petrogale differs from that of Macropus are :— 
(1) In Macropus the nasal bones have an equal breadth in their 
anterior two-thirds, the posterior third being only slightly broader. 
In Petrogale the nasals are much more slender in comparison and 
their posterior half is considerably broader than the anterior. 
(2) In Macropus the fronto-nasal suture comes farther back 
than the most posterior point of the fronto-maxillary in most 
cases. In Petrogale the condition is reversed. 
(3) In Macropus the zygomatic process of the maxilla projects 
downwards below the cutting-edge of the penultimate molar. In 
Petrogale it is seldom much lower than the alveolar margin of the 
maxilla, I am not inclined to iay much stress on this distinction, 
since it seems that the processes of the Kangaroo’s skull increase 
with age. 
(4) In my specimen of Petrogale the infra-orbital canal was double 
on both sides, a condition I have found in two out of five skulls. 
In Macropus the canal is oceasionally double on one side, but I 
have not found it so on both sides once in the thirteen skulls 
I have had the opportunity of examining. 
(5) In my specimen of Petrogale a Wormian bone (0s antiept- 
lepticum) was present at the junction of the coronal and sagittal 
sutures (see fig. 1, p. 685). This bone has been described by 
Gruber and Howes, and I am inclined to regard it as of some little 
classificatory value’. It occurred twice in the five skulls examined, 
and I have never seen it in any other Kangaroo. 
(6) In Petrogale the palatine process of the palate-bone is only 
represented by a narrow bridge marking the posterior boundary of 
the hard palate. In Macropus the palatine process is complete 
and the back of the hard palate has no perforation of any size. 
(7) The premaxilla of Petrogale is a larger bone in comparison 
with that of Macropus, and has not the sharp angle running back 
between the maxilla and nasal found in the latter. 
(8) The inter-parietal bone of Petrogale has a very different 
appearance to that of Macropus ; in the latter it is a more or less 
crescentic bone having a much greater breadth from side to side 
than from before backward, while in the former its antero-posterior 
measurement equals its greatest transverse, so that the bone forms 
either an isosceles triangle or a rough pentagon. 
(9) The paroccipital processes are better developed in Macropus 
than in Petrogale. 
As special stress is laid on the condition of the centres of 
ossification of the various bones, it will assist iu determining the 
animal’s age if the state of the teeth is noticed here. The anterior 
1 See the author’s paper on Atherura africana, P. Z.8. 1894, p. 677. 
