50 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
The third portion of the skull of Nototherium includes part of the right maxillary 
with three molars (d 4, m 1, m 2) in situ , and part of the right palatine bone (Plate IX. 
tigs. 6 & 7 ). The teeth are more worn than in the preceding specimen : the fossil is part 
of an aged individual ; the teeth, moreover, show a superiority of size compared with those 
of the last described fragment, answering to the difference one sees between the molars 
of the full-grown male and female Kangaroos. 
The hind surface of the maxillary pier of the zygomatic arch here lies vertically 
parallel with the fore half of the front lobe of m 2 : an extent of 3 inches 3 lines is 
preserved of the origin of the pier as it passes forward and upward, where the fracture of 
the maxillary traverses the interval between the sockets of d 3 and d 4. The bony palate 
arches upward and inward from the inner walls of the sockets of m \ and m 2, in as great a 
degree as from those of the socket of d 4. The extent preserved, in a straight line from 
the outlets of the alveoli, is 2 inches. The palato-maxillary suture begins at the inner 
or mesial fractured surface of the bony palate opposite the hind lobe of m 1 ; near the 
interval between m 1 and m 2 it extends outward and backward with an oblique curve to 
near the inner side of the outlet of the socket of m 2. Its relative position to the molars 
agrees with that of the palato-maxillary suture in Phascolomys latifrons ; in Macropus 
laniger the suture begins, mesially, at the transverse parallel of the interval between m 2 
and m 3, at least in an example with those molars in place and use. 
The palatine bone, like the maxillary alveolar tract, has been broken at the part 
behind m 2, the broad single posterior root of which is exposed. But at the fractured 
surface of the palatine there occurs, just opposite or parallel with the back part of m 2, 
a small tract of the natural smooth unbroken surface of the palatine, indicating a poste- 
rior palatal vacuity, on the parallel of m 3, as in Phascolomys. The thickness, vertically, of 
the fore part of the bony palate here preserved is 1 inch, of the hind part half an inch. 
In the younger, probably female specimens, the same admeasurements give 6 lines and 
2 lines. 
Contrasting the difference of size, shape, and relative position of so much of the max- 
illary zygomatic process and bony palate as is preserved in the two specimens just 
described, one is at first inclined to deem them to have come from different species of 
Nototherium ; and three species of the genus are indicated by mandibular characters. 
But in reference to the progressively backward extension of the zygomatic process of 
the maxillary, this may be coincident with the progressive growth of the alveoli of the 
hinder molars, as these teeth come into use ; in like manner, as their crowns are pushed 
down to the line of wear in the ratio of the abrasion of their wedge-shaped ridges, so 
the alveoli will cling to and follow the roots, growing as they lengthen, and giving a 
curve or concavity to the palatal surface not present or needed in the less worn condi- 
tion of m 1, m 2, and m 3, in younger individuals. 
With the foregoing evidences of the cranial characters of Nototherium we may safely 
proceed to bring them out, or add to their saliency, by comparison with those in other 
extinct and in existing Marsupialia. 
