BY R. BROOM. 71 



would lead us, moreover, to believe that there has probably been no 

 great change in the flora. 



It is probably, however, unnecessary to discuss further what 

 food Tliylacoleo could possibly have obtained, when we have, as I 

 hold with Owen, the most satisfactory proof from its anatomical 

 structure as to wdaat food it did obtain. It must be admitted 

 that Tliylacoleo had enormous temporal muscles, and it is perfectly 

 certain that such muscles would not have been developed unless 

 the animal required them. For what could such powerful muscles 

 be required 1 Most certainly not for slicing fruits or succulent 

 roots and bulbs, nor would they be required even for the slicing 

 of fleshy fibres. Temporal muscles are chiefly used apparently 

 for closing the jaws more or less forcibly from the open position, 

 while for the more complicated movements of mastication it is 

 the masseter and pterygoid muscles that are chiefly used. Hence 

 in all carnivorous animals the temporals are largely developed 

 and the maeseters more feebly, because the killing process 

 requires a very forcible closing of the jaws, and the work to be 

 done by the premolars and molars is comparatively little. 

 In herbivorous animals the conditions are reversed. The jaws 

 are here rarely required to be opened widely or to be closed with 

 any great force, while a very large amount of grinding work has 

 to be done, hence the temporals are rarely much larger than the 

 masseters and often vexy much smaller. When we look at 

 Thylacoleo we find not only the enormous temporals and only 

 moderate masseters, but everything else about the skull seems to 

 l)e built on carnivorous lines. Owen has shown the wonderful 

 similarity which exists between the molar machinery in Thylacoleo 

 and the lion, and it is hard to conceive as possible any other 

 cause giving rise to such a specialisation in Thylacoleo than that 

 which led to a similar specialisation in the cat tribe. Another 

 most striking feature is to be seen in the condition of the incisors. 

 Leaving out of consideration the mode of implantation and 

 structure of the teeth — both confirmatory of the carnivorous 

 hypothesis — there is one point which appears to me absolutely 

 conclusive on the subject. Unless Owen's figures are altogether 



