240 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA, 
With what molars are these scalpriform teeth associated ? Few, small, tubercular. 
Adapted for squeezing the soft animal nutriment out of the tegumentary covering of a 
caterpillar, not adapted for trituratory mastication of such vegetable food as calls for 
the more complex and massive molars of the Kangaroos, Potoroos, and Koalas. With 
what kind of teeth is the low-placed and backwardly placed condyle of Thylacoleo and 
Plagiaulax associated ? and what may be the diet indicated by such association ? For 
the response to these questions the palaeontologist, guided by the Cuvierian principle, 
refers to the great carnassial and the small tubercular molar teeth. 
§ 12. Comparison of the Mandibular Condyle in Thylacoleo , Plagiaulax, and Bodentia. 
— In placental Rodents the mandibular condyle is longitudinally horizontal, transversely 
convex ; its long diameter is from before backward ; it represents the section of a cylinder. 
The glenoid cavity of Thylacoleo shows that its condyle lias been convex from before 
backward or longitudinally, and with its long diameter transverse ; not limiting the 
jaw, as in Rodents, to horizontal movements chiefly to and fro, but adapting the jaw to 
hinge-like vertical motion, needed for the due action of the terminal laniaries and the 
large carnassials. 
The mandibular condyle in the more ancient and smaller Marsupials with a closely 
analogous dentition is demonstrably similar to that which is here inferentially ascribed 
to the condyle of Thylacoleo. It is in Plagiaulax convex longitudinally, or from before 
backward, and that in so great a degree that the most prominent part of the convexity 
looks backward. “ Its long diameter is disposed subvertically, and the outline is ovate or 
pyriform, the broad end being uppermost”*. This broad end is the transversely ex- 
tended part of the convex condylef. Dr. Falconer, nevertheless, affirms that the form 
of condyle presented by Plagiaulax is “ common in the placental Rodents ; yet is con- 
strained to add, “ with the difference, however, that in the latter the condyle having to 
work backwards and forwards in a groove, its articular surface is disposed longitudi- 
nally”^ 
But this difference precludes an ascription of community of form of condyle between 
Plagiaulax and Bodentia ; and in so far as the difference is such as to enable the con- 
dyle in Plagiaulax to work the jaw upward and downward, or vertically, it lends itself 
to those actions which the jaw has to perform “among the Carnivora 
The kind and degree of difference which the mandibular condyle presents in Chiromys 
and in Plagiaulax, already pointed out, in like manner illustrates its application in the 
latter to predatory actions, and is consequently and concomitantly associated with a dif- 
ference of form of the entire mandible : that part in Plagiaulax conforms with the 
lower jaw in Sarcojphilus and Thylacoleo in as marked a degree as it differs from the man- 
dible in Chiromys, in placental Rodents, in Phascolarctos, and in llypsyjrr minus. 
* X. p. 360 ; XI. p. 445. 
t Owen, Monograph on British Mesozoic Mammalia, pi. 4. fig. 10, A, c & B. 
J X. p. 360 ; XI. p. 445. § Id. ib. 
