PROFESS OK OWEN ON THE EOSSIL MAMMALS OF AUSTRALIA. 
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Thylacoleo, rises with a backward inclination to the highest, or vertically longest, part 
of the crown, from which a well-marked ridge traverses or forms the anterior margin of 
the crown (figs. 2 & 3, z). The anterior root is longer but narrower, antero-posteriorly, 
than the posterior one, as in the upper carnassial of Felines. 
In Hypsiprymnus minor (Plate XI. figs. 17, 18) the premolar has a straighter edge, 
not bilobed ; the outer side of the crown is indented with the four or more parallel 
grooves and ridges, at the apical half; the inner side is uniformly and obliquely worn, 
in degree according to age. 
§ 3. Mandible and Mandibular Teeth. — The portion of lower jaw (Plate XII. figs. 1-5) 
from the deposit at Gowrie includes 6 inches in longitudinal extent of the left ramus, 
viz. from the fore part of the symphysis (s) to the fore part of the strongly inflected 
angle (a). This latter character is acceptable as confirmatory of the marsupial nature 
of Thylacoleo , in a way more intelligible or convincing to some than the cranial and 
maxillary characters adduced in support of that induction in the original Memoir 
(Philosophical Transactions, 1859) ; although I am not aware that the marsupiality of 
Thylacoleo has been, by any objector, called in question. 
The fossil is massive, heavy, much petrified ; it retains the fang and base of the crown 
of the anterior and sole incisor (7), the entire carnassial (]> 4), and the two fangs of the 
anterior molar (fig. 3, m 1 ). 
The small and simple socket of the second molar is indicated (m 2 ) ; and two or three 
small and very shallow alveoli (Plate XII. figs. 2 & 3, p 3, p 2) intervene between the 
incisor-socket and the inner side of the anterior fourth part of the carnassial. From the 
condition of the upper small premolars it may be inferred that there were two or three 
similarly small functionless and speedily lost teeth between the carnassial and the lani- 
ariform incisor of the lower jaw, occupying the sockets (p 3, p 2, figs. 2 & 3). 
Assuming these to be three in number, the first and second are on nearly the same 
transverse line, so close together that the broken thin partition (1) gives the appearance 
of a single socket. 
The entire length of the alveolar tract is 3 inches ; from the back part of the last 
socket to the hind fractured end of the present fossil is 3 inches. As the extent 
from the fore part of the upper carnassial to that of the glenoid cavity in the skull 
figured in Plate 11 . & in., Philosophical Transactions, 1866, measures 5 inches 10 lines, 
it may be inferred that such must have been nearly, if not quite, the extent of the man- 
dible from the fore part of the lower carnassial to the fore part of the condyle ; con- 
sequently the entire length of the mandible would not be less than 7 inches. We may 
reckon that 1 inch, at least, is wanting from the broken hind part of the specimen figured 
(Plate XII.) ; and we may certainly infer that a greater proportion of the mandible was 
allotted to the joint and to the muscular forces working that instrument than to the 
dental weapons with which it was armed ; concentrated as they here are, as in the fellest 
Carnivora, for fatal efficiency. 
The symphysial contour (ib. figs. 1 & 2, s, r) rises from the lower border of the horizontal 
