After discussing numerous points in connection with the problem, Dr. Broom states that those who believe _Thylacoleo_ to have been carnivorous, “evidently consider that the molars have been reduced through their functions being taken up by the large premolars. But could the large premolars take up the molar function—could they grind? Even those who favour the idea of _Thylacoleo_ being a vegetable-feeder, admit that the premolars were cutting teeth, and the difficulty of imagining a herbivorous animal without grinders is got over by supposing that its food was of a soft or succulent nature.” But for the creature to have lived on succulent roots and bulbs, the vegetation of that part of Australia where it lived must, urges Dr. Broom, have been quite different from what it is at the present day; and we have no justification for assuming any such change to have taken place. Moreover, an animal that could only slice, and not grind up, vegetable food, could apparently subsist only on ripe fruit, and such is to be met with in Australia only at one season of the year, when, owing to the abundance of frugivorous mammals, little, if any, is allowed to fall to the ground. “It is probably however,” adds Dr. Broom, “unnecessary to discuss further what food _Thylacoleo_ could possibly have obtained, when we have, as I hold with Owen, the most satisfactory proof from its anatomical structure as to what food it did obtain. It must be admitted that _Thylacoleo_ 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? 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 masseters 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 very 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 be 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