1868.] FLOWER THTLACOLEO. 309 



Professor Owen described and figured a more complete skull, belong- 

 ing to " the same large carnivorous marsupial." The specimen was 

 obtained from " that part of the freshwater deposits of Darling 

 Downs through which the river Condamine has cut its bed." The 

 additional evidence afforded by the more perfect condition of the 

 specimen appears to have modified Professor Owen's views as to 

 the affinities, though not as to the diet and habits, of the animal, 

 '* Thylacoleo^^ we now read, " exemplifies the simplest and most 

 effective dental machinery for predatory life and carnivorous diet 

 known in the mammalian class. It is the extreme modification, to 

 this end, of the Diprotodont type of Marsupialia. Besides the full 

 confirmation which the additional fossils here described give of the 

 marsupiality of Thylacoleo, its closer affinities in that order are 

 shown to be, not to the existing carnivorous marsupials, e. g. Sar^ 

 cophilus, Dasyurus, Tliylacinus, Didelphys, but to the Diprotodons, 

 Nototheres, Koalas, Phalangers, and Kangaroos." 



Beyond this incomplete cranium and mandible, nothing is at pre- 

 sent known with certainty of the structure of this remarkable ani- 

 mal *. But from the information contained in the above-quoted 

 memoirs, with some additional observations derived from the exami- 

 nation of some more recently received fragments in the British 

 Museum, and part of a mandible (from the Wellirigton Yalley) in 

 the Museum of the College of Surgeons, the dental characters are 

 sufficiently apparent to enable us to draw with tolerable certainty 

 all such conclusions as to affinity, food, and general mode of life as 

 may legitimately be derived from the study of this most important 

 part of its organization. 



The first subject upon which the attention will naturally be en- 

 gaged when any new object of this nature is brought to light is 

 a comparison with already known forms, with a view to ascertain 

 to which of them it most nearly approximates. This inquiry must 

 precede any purely deductive speculations as to its characters or 

 purpose. 



The most striking feature in the dentition of Thylacoleo (see fig. 1, 

 p. 312) is the single hugec ompressed trenchant premolarf tooth in 

 either jaw. This tooth alone, interpreted by a mere empirical com- 

 parison with teeth of known animals, appears sufficient to furnish 

 the key to the whole question at issue. Professor Owen, naturally 

 pursuing this method of proceeding, fixed upon the so-called " sec- 

 torial," or "carnassial" tooth of the Lion as its nearest simihtude 

 among mammalian teeth, and has ever since spoken of it as a " sec- 

 torial " or " carnassial," and assigned corresponding functions to all 

 the other teeth. It was the examination of this same tooth, result- 

 ing in finding that it agreed more closely with a tooth of a very 

 different animal, that has lead me to another conclusion. 



That the resemblance of the great premolar of Thylacoleo to the 



* That the metacarpal bone figured in the Phil. Trans. 1859, pi. xiii. belonged 

 to the same animal as the skull, is only conjectural. 



f So called from its apparent homology with the posterior premolar of the 

 recent marsupials. 



