139 



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 VII. 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. 



Mandible and Mandibular Teeth. — The portion of lower jaw (Plate VIII. 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 (i), the entire carnassial (p 4), and the two fangs of the 

 anterior molar (fig. 3, m 1). 



The small and simple socket of the second molar is indicated (in 2) ; and two or three 

 small and very shallow alveoli (Plate VIII. 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 (?) 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 Plates XVI. & VII., measures 5 inches 10 lines, it may be inferred that such 

 must have been nearly, if not quite, the extent of the mandible from the forepart of the 

 lower carnassial to the fore part of the condyle ; consequently 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 VIII.) ; 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 



