PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
185 
These five ever-growing teeth gain in fore-and-aft as in transverse diameter, until the 
full size of the individual is attained ; they grow with the growth of the skull, though 
in a minor ratio ; and I have no evidence of their exceeding in size the teeth requiring 
the extent of alveoli noted in the largest of the cranial specimens of Phase, vombatus 
before me. 
Now in this, as in the second-sized skull, the lower border of the malar process of the 
maxillary bone is 6 lines above the margin of the outer wall of the alveolar opening of 
to 2 ; in the younger and smaller skull it is 5 lines. In all the specimens the maxillary 
contributes to the inner and lower part of the beginning, or anterior pier, of the zygoma, 
speedily narrowing to a point as it passes backward on the outer side of the arch, where 
it ends about 7 lines from the back part of the origin of the process ; the depth or ver- 
tical diameter of the outer side of the base of the zygomatic process of the maxillary is 
about 2 lines. 
In the skull of a Pliascolomys latifrons with an upper molary series, taken at the 
alveolar outlets, of 1 inch 10 lines in extent, the malar process of the maxillary rises 
7-§- lines above the issue of the second molar, there contributes 3£ lines in depth to the 
under and fore part of the beginning of the zygoma, and narrows to a point 7 lines behind 
its origin. In another skull of Pliascolomys latifrons with a molary series of 1 inch 
1 line in extent, the maxillary process rises 8 lines above the outlet of the second molar, 
and contributes a similar small proportion to the under and fore part of the zygoma. 
In the skull of a Pliascolomys platyrliinus with a molary series 2 inches 1 line in extent, 
the malar process of the maxillary (Woodcut, fig. 5, 21 *) rises 6 lines above the outlet of 
the second molar, and contributes 3-| lines to the vertical extent of the beginning of the 
zygoma ( 20 ), which here has a total depth of 1 inch 4 lines ; the process ( 21 *) decreases to 
a point at 9 lines from its origin. 
In the fossil (Plate XVIII. fig. 5) with a molary series of the same extent as in the 
last skull, the malar process of the maxillary ( 21 ) rises 9 lines above the outlet of the 
molar, and contributes 7 lines to the vertical extent of the fore part of the zygoma ( 26 ). 
The different relation of the malo-maxillary suture to the premasseteric ridge (to) is 
strongly marked between the fossil and any of the recent species of Wombat, the 
interspace between the front pier of the zygomatic arch and the alveolar outlets being 
much greater in the fossil. 
In the extent, especially hinder breadth and feeble concavity, of the bony palate, Plias- 
colomys platyrliinus most resembles the present (ib. fig. 7) as it does the preceding fossil; 
but the zygomatic character only stands out the more strongly in connexion with this 
resemblance and the general size. 
In Pliascolomys vombatus the form of the palate resembles that in Pliascolomys pla- 
tyrliinus. It is rather more concave in some individuals than in others in both species ; 
and in the Platyrhine Wombat I have noticed a slight mesial ridge along the bony palate. 
In Pliascolomys latifrons the palate is not only more concave, but is wider anteriorly, 
less triangular ; and at the hind part formed by the proper palatine bones, their median 
