PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
251 
that feature of the mandible of the Megatliere, and it has a like relation to the 
lodgement of the formative matrices of long, ever-growing molars 
The first molar (ib. figs. 1 & 3, d 3) is subbilobed, through opposite longitudinal shallow 
grooves equally dividing the tooth. The tendency to a gain of grinding-surface in the 
direction of the jaw’s axis seen in the same tooth of Phascolomys medius is in the larger 
species carried further, so as to substitute for the representative of one half or lobe of 
the succeeding molars in the anterior one of smaller Wombats a more simplified con- 
dition of the normal bilobed pliascolomydian type of molar. The enamel of d 3 in 
Phascolomys gigas is continued from the outer over the front side, and along nearly the 
whole of the hind side of the tooth. A coat of cement of similar thickness covers trie 
inner side, and is continued more thinly upon the enamel. The surface of the enamel 
is longitudinally rugoso-striate. 
All the succeeding molars have a partial coat of enamel, extending from the outer 
side upon the fore part to where this comes into contact with the antecedent tooth, and 
continued, perhaps, a little further upon the hind surface. The rest of the dentine has 
the coating of cement. The proportions of the several teeth are shown in the figures 
above cited. 
As before remarked, the smaller size of the last molar indicates the Latifront Wombat 
to be nearer akin to the extinct giant than are the bare-nosed livinq- species. The 
same affinity is shown by the small size of the lower incisors in Phascolomys gigas 
(Plate XL. figs. 1, i, 2, 3, 4). They are smaller, especially narrower, in Phascolomys 
latifrons than in Phase, platyrhinus and Phase, vombatus, and are, relatively, still 
smaller in Phase, gigas , with a distinctive shape. But the characters of the lower pair 
of incisors are better shown in another mandibular specimen of the present large species. 
The section or transverse fracture of the hollow base of the right incisor is shown in 
Plate XXXVII. fig. 2, i ; the length and curvature of the implanted part of the second 
molar ( d 4) are seen in the same figure, in which e e indicates the anterior terminal line 
of the outer enamel. The hinder fracture of the left ramus of the same jaw (ib. fig. 3) 
shows the length and curve of the penultimate molar (to 2), and the posterior terminal 
line of its partial covering of enamel (e). 
Of the above-described instructive specimen of Phascolomys gigas little more than an 
inch of the diastemal part of the jaw is preserved (Plate XXXVI. figs. 1 & 2, /). Fortu 
nately, the first specimen which made known to me the fact of so large a W ombat having 
formerly existed in Australia included 2 inches 8 lines of the diastemal part of the jaw, 
which contracts rapidly to the terminal outlets of the incisive alveoli (Plate XXXIX. 
figs. 1 & 2) ; whence I conclude that but little had been broken away from that end of 
the mandible. 
* Should any successor deem the differential characters of the giant "Wombat of generic or subgencric value, 
as the minor differences of Phascolomys latifrons have been by Dr. Murie (Proc. Zool. Soc. 1367, p. 815), they 
may, perhaps, accept the name ‘ Phascolonvs,’ having reference to the size of this species, which equalled that 
of the Wild Ass. 
2 L 2 
