1868.] FLOWER THYLACOLEO. 315 



The cousideration of this subject involves a glance at the whole 

 (question, as to whether, and, if so, within what limits, the cha- 

 racters of an animal's teeth afford a guide to a knowledge of the 

 nature of its food and general habits. Although it may be asserted 

 broadly that certain strongly marked forms of dentition are con- 

 stantly associated with the function of seizing and masticating cer- 

 tain kinds of alimentary substances, there are so many instances of 

 allied animals having very different dietetic habits without any 

 corresponding modification of dental structure (to take the well- 

 known case of the Bears, for example), that too much caution cannot 

 be exercised before pronouncing a positive opinion in regard to any 

 newly discovered form the habits of which are totally unknown, as 

 is necessarily the case with an extinct animal. I think, however, 

 that the following proposition will be generally accepted as the first 

 step in the process of forming a conclusion upon the subject : — That 

 if all the known species of a large group of animals with teeth 

 formed upon one peculiar type lead lives peaceable and inoffensive to 

 their neighbours, and feed mainly on vegetable substances, the pro- 

 babilities, in the case of any newly discovered species having 

 teeth constructed upon the same general type, are greatly in favour 

 of its having possessed similar habits, and been nourished by a cor- 

 responding diet. 



To apply this to the present case, it is a well-known fact that all 

 the animals belonging to the families Macropodidce* and Phalan- 

 gistidcef, including upwards of seventy species, are in the main 

 phytophagous, feeding either on grass, roots, fruits, buds, or leaves, 

 the larger proportion of them exclusively so, though a few (the 

 arboreal Phalangers) are said also to partake occasionally of insects 

 and small birds. Not one of the group is known to be exclusively 

 carnivorous, or ever to attack or destroy animals approaching to 

 itself in size. 



The presumption in the case of Thylacoleo is, therefore, that it 

 was also a vegetable feeder ; and this presumption can only be over- 

 ruled by pointing out some special modifications of its dental struc- 

 ture of such a nature and extent as to warrant our inferring a total 

 subversion of the habits of its congeners. 



In order to test how far such modifications have been shown to 

 exist, I will cite Professor Owen's principal arguments for the pre- 

 datory nature of this animal. " In existing carnivorous mammals," 

 he says, '' the ferocity of the species is in the ratio of the ' car- 

 nassiality ' of the sectorial molar, i. e. of the predominance of the 

 * blade ' over the ' tubercle ;' and this ratio is shown more particu- 

 larly in the upper sectorial, in which, as the tubercular part enlarges, 

 the species becomes more of a mixed feeder, and is less devoted to 

 the destruction of living prey. From the size and form of the car- 

 nassials of Thylacoleo, especially of the upper one, we may infer that 



* Equivalent to Prof. Owen's division Pocphaga, or " Grass-eating " Mar- 

 supials. 



t Equivalent to Prof. Owen's Carpophaga, or "Fruit-eating " Marsupials. 



