542 ON DIPROTODON 
the maxilla slopes directly outwards and backwards from the infra- 
orbital foramen to form the prominent anterior margin of the orbit. 
In Zygomaturus the zygomatic process of the maxilla is given off at 
a point where the surface of that bone is quite smooth in the fossil 
before us. 
Of No. 2 (Pl. XXI. [Plate 38] figs. 4, 5, 6), a left maxilla, less of the 
upper and anterior, and more of the posterior and inner part, remain. 
The floor of the infraorbital foramen remains, and exhibits the same 
rapid slope as that of the other specimen. A strong horizontal palatine 
process is given off from the inner side of this fragment of the left 
maxilla. Its greatest breadth is one inch and three-eighths ; and its. 
inner boundary, rough and broken, presents no indication of a suture, 
so that the palate had more than double this width at this point. 
Opposite the interval between the first and second molars a small 
canal opens forwards, upon the under and anterior surface of the palate 
opposite the premolar. The palatine plate is three-eighths of an inch 
thick, and presents a flat external division, separated by a ridge from 
an inner part which slopes somewhat upwards; but behind the 
opening of the canal just mentioned, the under or oral surface rises 
both inwards and backwards; and the upper or nasal surface falling 
in the same proportion, the palatine plate ends posteriorly and inter- 
nally, opposite the interval between the second and third molars, ina 
thin edge, which, in this specimen, is nowhere completely entire. In 
a specimen of the right maxilla of Dzprotodon, containing all the teeth 
save the premolar, in the collection of the British Museum (marked 
32858), to which I shall have occasion to make frequent reference, the 
palatine plate is seen to end in a free, thin, rounded edge, and to become 
narrower from the level of the commencement of the third molar ; so. 
that, no doubt, a great palatine vacuity existed at this spot. This 
is the more remarkable, as, judging from a cast in the same col- 
lection, the palate of Vototheriuim was entire, and extended, as in the 
Kangaroos, behind the last molar tooth. 
The molar teeth have the general characters of those of the lower 
jaw of Dzprotodon already described by Professor Owen. Each 
exhibits two principal transverse ridges, with a posterior almost 
obsolete, and an anterior, much more prominent and thick, but still 
low, basal ridge. The principal ridges are directed transversely to the 
axis of the palate and the alveolar margin, or have, at most, but a very 
slight inclination backwards and inwards. They are slightly concave 
backwards ; and they wear down at first into two oval or elongate- 
reniform facets, separated by a deep valley, whose outer ends are, 
as usual, higher than the inner. The tooth becomes abraded faster 
in front than behind,—the anterior basa] ridge contributing a single 
