52 Mr. Owen on the Thylacotherium. 



described by Mr. Broderip, the entire process, and consequently the angle of the 

 jaw, which in the Marsupials constitutes this process, is broken away : in this 

 jaw, likewise, the gentle convex line, continued from the condyle into the lower 

 margin of the horizontal ramus of the jaw, is uninterrupted, precisely as in the 

 jaw of the Marsupial {Dasyurus viverrinus) now on the table*, in which I have 

 broken away, in a similar manner, the inwardly produced angle. In the fossils, 

 something which projected inwards has evidently been broken off. The very cir- 

 cumstance of the angular process projecting inwards beyond the plane of the 

 ramus of the jaw, would render it most liable to be broken off when the matrix 

 came to be detached from the inner surface of the jaw ; whereas, if it had been 

 simply continued backwards, it might have been preserved entire ; but this has 

 not been the case in any of the fossils hitherto obtained from Stonesfield. 



These appearances, in conjunction with the condyloid and coronoid processes 

 forming parts of one simple, continuous, undivided plate of bone, would be 

 sufficient to determine, not only the mammiferous, but the carnivorous, and to 

 strongly indicate, in the Phascolotherium at least (PI. VI. fig. 2), the marsupial 

 nature of the Stonesfield fossils, if even every tooth and alveolar process had been 

 destroyed. 



Nevertheless, in a question of so much interest in the problem of the order of 

 appearance of animated beings on our planet, it is well that these parts also are 

 present, and in sufficiently good preservation in the fossils in question to yield im- 

 portant auxiliary proofs of their mammiferous, if not marsupial nature. 



M. de Blainville alludes to a careful drawing of one of these jaws which 

 represented the posterior molars as having "la forme en palmette, quinque- 

 lobee," a form which he observes is sufficient to expel them not only from the 

 marsupial but the mammiferous series. To this it may be replied, that certain 

 species of Seal, both recent and fossil, might, for the same reason, be argued to be 

 non-mammalian. 



The following is the exact condition of the teeth in the specimen of the Thylaco- 

 therium examined by Cuvier (PI. V. fig. 3) : — there are ten molars in situ, each 

 with two fangs imbedded, as the seven anterior molars show, in deep and distinct 

 sockets ; there is an evident trace of the sockets of another molar anterior to 

 those in place. 



The molars very gradually increase in size from the first or anterior one to the 

 sixth in the present specimen ; the rest are equal, except the last, which is some- 

 what smaller. The crowns of all the grinders, except the second, third andfourthf, 



* This specimen is now placed by the side of the jaw of the Phascolotherium in the British Museum, 

 t The teeth are here enumerated as they exist in the fossil, not with reference to the true dental for- 

 mula. 



