PROFESSOR. OWEN ON THE EOSSIL MAMMALS OF AUSTRALIA. 
49 
It shows part of the front pier of the maxillary arch, including its posterior surface, 
which springs from the alveolar plates on the vertical parallel with the interval between 
the two lobes of m i, at its lower end, and extending as it rises with a curve convex back- 
ward to overhang part of the hind lobe of the same tooth. Sufficient of this maxillary 
zygomatic process remains to exemplify the difference between Nototlierium and Dipro- 
todon in the antero-posterior extent or thickness of this “ pier it is characteristically 
greater in the smaller Herbivore, and of itself would save the palaeontologist from 
being led astray by the close general resemblance of the upper molars of Nototlierium 
with those of Diprotodon. The present fragment being from a young specimen, the 
dental lobes show well their vertical curve concave forward, and the transverse curve of 
the edge of the wedge concave backward. I availed myself of this fragment to expose 
the front roots of the anterior molar and the hind root of the posterior molar ; but these, 
with other dental characters, will be noted in the section on the teeth of Nototlierium- 
The present specimen afforded the subj ect of fig. 8 in Plate IX. : it shows a part of 
the convex roof of the alveolar tract which projects into the orbito -temporal vacuity, 
and the contiguous groove for the superior maxillary nerves and vessels. 
The second cranial specimen is a larger proportion of the left maxilla with three 
molars in situ (d 4, m 1, m 2), part of the socket of the first (d 3), and the base of the crown 
of the last {in 3) rooted in its socket. 
A portion of the bony palate extends with a slight upward curve, inward, from the 
sides of the sockets of d s, d 4, and more distinctly inward from those of m 1 and m 2 . A 
breadth of 1 inch 6 lines is preserved (opposite d 4 ) : the fracture reduces the breadth to 
6 lines as it extends backward to the alveolus of m 3. So much as is preserved of the 
bony palate confirms the inference of the entireness of the bony roof of the mouth 
deducible from the cut and photograph of the entire cranium, as far back at least as the 
sockets of m 3, right and left. The hind part of the origin of the zygomatic process of 
the maxillary is here at the vertical parallel of the interval between m 1 and m 2 , con- 
sequently rather further back than in the former fragment. The worn surfaces of m 1 
and m 2 show the present to have come from an older individual, as will be subsequently 
pointed out in detail. An extent of 3 inches of the massive maxillary pier, as its origin 
extends from behind obliquely upward and forward, is here preserved ; the thickness of 
the process is 1 inch 3 lines. The height of the alveolar process or tract at the last two 
molars is 2 inches 9 lines. The transversely convex or arched roof of these sockets is, 
relatively, less broad and prominent than in the Wombat; its extent and proportions 
resemble more the corresponding part in the Kangaroo, conformably with the common 
character of three-rooted teeth of limited growth, which contrasts with that of the large 
undivided bases of the corresponding molars in Pliascolomys , retaining their formative 
matrices, and making a proportional prominence outside the “superior maxillary chan- 
nel.” This channel in Nototlierium describes a curve convex outward as it courses 
forward to perforate the antorbital part of the maxillary and emerge upon the outer 
surface of that bone (as the ‘antorbital foramen,’ 21 , fig. 1, Plate II.). 
MDCCCLXXII. h 
