PEOFESSOR OWEN OX THE FOSSIL 3IAMMALS OF AUSTEALIA. 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 e-vidence of their exceeding in size the teeth requiring 

 the extent of alveoli noted in the largest of the cranial specimens of Phase, vomlatus 

 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 

 ?/i 2 ; in the younger and smaller skull it is 5 lines. In all the specimens the maxillaiy 

 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 Phascoloiwjs 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 Phascolomys latifrons with a molary series of 1 inch 

 1 line in extent, the maxillaiy 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 Phascolomys plati/rhini'.s with a molary series 2 inches 1 line in extent, 

 the malar process of the maxillary (Woodcut, fig. 5, 2i») rises G lines above the outlet of 

 the second molar, and contributes 3^ lines to the vertical extent of the beginning of the 

 z}'goma (26), which here has a total depth of 1 inch -i lines ; the process (2i«) decreases to 

 a point at 9 lines from its origin. 



In the fossil (Plate XYIII. 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 difierent relation of the malo-maxillary suture to the premasseteric ridge (i7i) 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, Phas- 

 colomys plat ijrhinus 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 Phascolomys vombatus the form of the palate resembles that in Phascolomys pla- 

 tyrhinus. It is rather more concave in some indiriduals than in others in both species ; 

 and in the Platyrhine Wombat I have noticed a slight mesial ridge along the bony palate. 



In Phascolomys 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 



