318 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 8, 



devouring a beetle is totally different from that of a cat in seizing 

 and killing a rat or a rabbit ; and the dental structure is suited 

 to each case. In many of the smaller Dasyures, as well as in some 

 Lemurs, which are more or less insectivorous in their habits, there 

 is generally a tendency to enlargement of the central incisors. 



There are also animals which, belonging to groups generally 

 phytophagous, and with teeth constructed on much the same pattern 

 as the rest, may on occasions be more or less predatory and carnivo- 

 rous, as in the well-known case of the Eat, among Rodents*. But 

 then, how inferior is the development of these qualities in such an 

 animal, compared with a true carnivore of corresponding size ! How 

 mild is the ferocity and destructive power of the most predatory of 

 Rats compared with that of its enemy the Ferret ! 



The interpretation of the function of the hinder teeth of Thyla- 

 coleo is certainly not easy ; as a herbivore with rudimentary true 

 molars is almost as anomalous as a carnivore without canines. 

 There is, however, no reason to suppose that the large trenchant 

 premolars were not as well adapted for chopping up succulent roots 

 and vegetables as for " dividing the nutritive fibres " of animal 

 prey. 



What was the particular form of food associated with the most 

 singular dentition of Thylacoleo, it would be hazardous to do more 

 than conjecture. As the flora of the country in which this strange 

 animal existed has probably undergone as great a change as the 

 fauna, it is not unlikely that the material upon which it subsisted 

 has passed away with the creature itself. It may have been some 

 kind of root or bulb ; it may have been fruit ; it may have been flesh. 

 But the hypothesis that Thylacoleo was the destroyer of the gigantic 

 herbivorous marsupials (many times as large as itself) with which its 

 remains are found associated, the Diprotodons and the Nototheres, 

 appears to me to require more proof than has yet been adduced in 

 its favour. 



What the remaining portions of this interesting animal were like, 

 and whether its hind foot was constructed upon the syndactylous 

 type with which the diprotodont form of dentition is at present 

 always associated, remain to be proved by the result of further 

 explorations in the country which has already yielded so rich a 

 harvest of palseontological novelties. That the Posttertiary de- 

 posits of Austraha should supply forms more or less allied to those 

 now inhabiting the same land is only what might be expected ; 

 but that in the vastly distant ages of the deposition of the Purbeck, 

 or still older Rhaetic bedsf, mammals should have existed with 

 teeth constructed on the same or a closely similar and equally 

 specialized type is a circumstance of much wider interest to the 



* The fact that such exceptions occur only shows the caution that should be 

 exercised in positively assigning a particular mode of life to an animal whose 

 habits are unkaown. We cannot by their aid justify an inference which 

 is proved to be at variance with the larger proportion of known analogies. 



t " On the Discovery of a new Fossil Mammal in the Grey Marls beneath the 

 Bone-bed" {H'/psiprf/mnop&is Fhtsticus), bv W. B. Dawkins. Quart. Journ. Greo]. 

 See. 1884. p. 4(K». ■' " - . 



