344 Prof. Owen on the Skull o/ Thylacoleo carnifex. [June 15, 



loped temporal muscles, as in Felis. In the lower jaw there is, anterior to 

 the carnassial, either a socket for a small double-rooted premolar, or two 

 approximate sockets for as many single-rooted ones ; and, as in the upper 

 jaw, these cavities do not range in the same longitudinal line with the 

 carnassial, but extend obliquely inward and forward, from the inner side 

 of its fore part. There is no other alveolus in the lower jaw between the 

 premolar one and that of the large lower tusk. The small 'tubercular' 

 molar on the inner side of the hind end of the upper carnassial, and the 

 two ' tuberculars ' behind the lower carnassial, are indicated by their sockets 

 in the present specimen. The author sums up, from acquired data, the 

 dental formula of Thylacoleo as follows : Incisors j^, Canines \ t Pre- 

 molars J^| or g, Carnassials J^j, Tuberculars . Of the incisors, the 

 foremost above are long and large tusks, like the pair below : of the other 

 teeth, the carnassials, of unusually large size, are functioned as flesh-cutters, 

 and the small tuberculars would serve for pounding gristle or tendon, as in 

 Felis : the premolars indicated by sockets, and the small upper incisors, 

 represent a remnant of the dental family type under its extreme adaptive 

 modifications in Thylacoleo. 



In the rest of the skull of the subject of the present Part, many particu- 

 lars are yielded in addition to those deduced from the fragmentary fossils 

 which indicate the genus. They confirm the deductions of the marsupial 

 nature of the large extinct Australian carnivore ; determine the alternative 

 expressed in the author's first communication as to the homologies of the 

 inferior tusks, and show that the genus Thylacoleo ranges, not with 

 the series now including Didelphys, Dasyurus, and Thylacynus, but with 

 the Diprotodont group, more eminently characteristic of the Australian 

 continent, and which is at present represented by, or reduced to, the genera 

 Phascolarctos, Phalangista with its subgenera, Macropus with its subgenera, 

 and Phascolomys. The carnassial of Thylacoleo, in its large proportional 

 size, absence of the tubercular part, and indications of subvertical groovings 

 of the enamel, most closely resembles that tooth of the more ancient mar- 

 supial carnivore Plagiaulax, and is associated, in the lower jaw, as in that 

 genus, with two small posterior tuberculars, one or two small premolars, 

 and one large incisive tusk, similarly directed obliquely upward and forward. 

 Few facts in mammalian palaeontology are more interesting and suggestive 

 than the occurrence in our hemisphere, during secondary geological periods, 

 of Marsupial forms, which find their nearest representatives in existing or 

 tertiary extinct Marsupialia of the continent of our Antipodes. 



The present Part of the author's series of Papers on Extinct Australian 

 Mammals is illustrated with drawings of the entire skull of the Thylacoleo 

 carnifex. 



