1865.] DR. J.MURIE ON THE SPECIES OF PHASCOLOMYS. 847 
parative agreement there is between these three in measurements, 
and in what respects they differ from those of P. wombat. 
Before summing up the marks which seem to indicate or serve asa 
means of distinguishing the skull of P. platyrhinus from that of P. 
wombat, itis proper I should dwell for a moment upon some observa- 
tions on the skull of this last species made by Dr. Gray (Proc. Zool. 
Soc. 1847, p.41). I must, however, with due deference to that natu- 
ralist, acknowledge my ignorance of his paper until my attention had 
first been directed to some of the differences which he so concisely 
indicates. In his paper he points out that three crania of Wombats 
in the British Museum vary from each other in several particulars. 
Two of these, from Van Diemen’s Land, are much smaller, more de- 
pressed and truncated behind, and have two moderate-sized oblong 
postpalatine foramina ; the third specimen, from New South Wales, 
is altogether bigger, and has two large triangular postpalatine 
foramina ; while all three disagree in the relative position and size 
of their upper incisors. 
These differences he attributes to individual variation, although 
suggesting that more than one species might be confounded under 
the same name. We see from this that Dr. Gray, without exactly 
admitting specific distinction, yet was the first to call attention to 
several of the diagnostic peculiarities of P. platyrhinus. 
The chief specialities, therefore, which seem to serve to distinguish 
the skull of P. platyrhinus, are these four :—the greater size of the 
cranium, the greater relative breadth of the nasal bones, the mode- 
rately deep tympanic excavation, and more triangular form of the 
posterior palatine foramina as compared with that of P. wombat. 
In P. latifrons the supratympanic cavity and postpalatine fora- 
mina are still larger than in P. platyrhinus, especially the latter in 
one of the specimens examined. In P. platyrhinus the columella, 
composed of the two conjoined inner edges of the horizontal plates of 
the palatine bones, is intermediate in thickness between those of P. 
latifrons and P. wombat, the last having it the stoutest. Professor 
Owen* says that these foramina “deserve particular attention, as 
they are generally specific.” 
The more depressed truncation in the skull behind, as observed 
by Dr. Gray in P. wombat, may be due to age; but it is note- 
worthy that in the adult of P. platyrhinus there are two very 
marked backwardly produced supraoccipital crests, and these are 
much stronger in every way than in the largest specimen of P. wom- 
bat that I have seen. 
In P. platyrhinus the two squamous portions of the temporal 
bones are relatively shallower than in P. wombat, while P. lati- 
Jrons has them most prominent and convex. 
Both in P. wombat and P. platyrhinus the upper incisors pre- 
sent an internal longitudinal furrow; P. platyrhinus, besides, has a 
longitudinal groove upon the external surface near the posterior 
angle, which I do not find in P. wombat, excepting very slightly 
in one specimen in the College of Surgeons, where it is almost dis- 
* Trans. Zool. Soe. vol. ii. p. 388. 
