PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
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position to the hind lobe of m 1 . The enamel in all the molars is longitudinally striate, 
the striae being feebly marked and subrugose. 
Completing the upper molar series according to the analogy of Phascolomys latifrons , 
its antero-posterior extent would be about 2 inches 8 lines ; and this is the extent shown 
in a photograph (Plate XXXV. fig. 7), nat. size, of a portion of the upper jaw of Phas- 
colomys medius , with the entire molar series of the right side, from the breccia-cave of 
Wellington Valley, New South Wales, in the Australian Museum, Sydney, for which I 
am indebted to the Trustees of that Museum and their able Curator, Mr. Krefft. 
The margin of the diastemal part of the upper jaw (Plate XXXII. fig. 2, l) is sharp 
to near the incisive outlets (if where it broadens and becomes obtuse. The cross section 
of the incisor (ib. fig. 6) is a transverse oval, 6 lines in long diameter, 4L lines in short 
diameter ; the small end of the oval is obtuse and turned outward. The enamel bends 
from above a very short way down upon the inner side or large end of the oval ; it arches 
down over the small end. The enamelled surface of the tooth is more convex than 
the hind orlower cement-clad surface ; but this is more convex, or less flattened, than in 
Phascolomys latifrons. The long and short diameters of the transverse section of the 
incisor in the other two living species are in opposite directions to those in the present 
fossil and the Latifront Wombat. 
In Phascolomys medius the malar process of the maxillary (Plate XXXII. fig. 3, 21 *) 
rises thirteen lines above the alveolus of the third molar : the intervening wall of the 
maxillary is moderately concave vertically ; in the smaller living Wombats it is convex ; 
but in the character of height of origin of the process we again have an evidence of 
affinity to the latifront species. The photograph (Plate XXXV. fig. 7) shows a close 
correspondence with the fossil in this character. 
The prezygomatic ridge (Plate XXXII. fig. 3, m) is low and broad, but in course and 
length resembles that in Phascolomys latifrons ; in Phase. plat yrhinus this ridge is shorter, 
relatively thicker, and more prominent. Anterior to the ridge and the socket of d 3 the 
maxillary part of the skull of Phase, medius contracts transversely, seemingly more 
suddenly than in existing Wombats, to form the diastemal part of the upper jaw. The 
maxillo-premaxillary suture runs vertically, with a sinuous and strongly denticulate 
course, about 5 lines in advance of the socket of d 3. The front walls of the incisive 
sockets (Plate XXXII. figs. 3, 4, & 5, 22 , 22 ) are relatively higher or deeper than in Phas- 
colomys latifrons , in which they are relatively higher than in the bare-nosed Wombats. 
The contour of this part of the premaxillary is rather concave in the fossil. 
The photograph above referred to (Plate XXXV. fig. 7) of the cave fossil shows the 
same depth and shape of the bony palate, and the same somewhat abrupt contraction 
of the diastemal part of the maxillary, as in the fossil (Plate XXXII. fig. 2) from 
Eton Vale. 
These evidences of specific distinction, superadd ed to the marked superiority of size of 
Phascolomys medius , are acceptable ; although the degree of constancy of size and shape 
of teeth in the three species of living Wombats would have justified an inference, from 
2 k 2 
