

ITS DISPUTED AFFINITY. 437 



Professor Owen draws an argument, in confirmation of his 

 view, from the dentition of Thylacoleo. The statement is : 

 — ■' In Thylacoleo the lower canine, or canine-shaped incisor, 

 projected from the fore-part of the jaw, close to the sym- 

 physis ; and the corresponding tooth in Plagiaulax more 

 closely resembles it in shape and direction than it does the 

 procumbent incisor of Hypsipryvn/n/us. 3 l But on referring to 

 his detailed description of Thylacoleo, we find that the body 

 of the tooth, of which the shape and. direction are adduced 

 as terms of comparison, together with the fore part of the 

 symphysis and incisive border, is wanting 2 : — ' The symphysis 

 (PI. XIII. fig. 4, s) begins behind, at a vertical line dropped 

 from a little in advance of the middle of the sectorial, p 4 ; 

 it is of a wide and oval form. To judge from the cast, but 

 little of the jaw appears to have been broken away from the 

 fore-part of the symphysis. The upper and fore-part shows 

 the alveolus and base of a tooth (PL XL fig. 3, c) which has 

 projected obliquely upward and forward. It is separated by 

 an interspace of three lines from the sectorial, and would seem 

 to be the sole tooth in advance of it. If the ramus be really 

 produced at the upper part of the symphysis further than is 

 indicated by the present cast, it may have contained one or 

 more incisors, and the broken tooth in guestion may be the 

 lower canine. If, however, this be really the foremost tooth 

 of the jaw, it would appear to be one of a pair of large in- 

 cisors, according to the Marsupial type exhibited by the 

 Macropodido3 and Phalangistida}.'' 3 ' But in the lower jaw 

 the carnassial is succeeded by two very small tubercular 

 teeth, as in Plagiaulax ; and there is a socket close to the 

 symphysis of the lower jaw of Thylacoleo, which indicates 

 that the canine may have terminated the dental series there, 

 and afforded an additional feature of resemblance to the 

 Plagiaulax.' 4 



In all this, it will be seen, the argument is within the do- 

 main of conjecture ; the tooth oscillates between canine and 

 incisor ; and not merely so, but the principles which are fol- 

 lowed as guides in this walk of investigation are set aside, 

 to give place to the illusory indications of mutilated external 

 form. If the tooth represented by a stump or socket proves 

 to be a canine, the comparison will not hold ; but if it be 

 solitary with the position of an incisor, will it even then bear 

 out Professor Owen's hypothesis, that Thylacoleo, which he 



1 Paleontology, p. 353. 



2 ' Unfortunately this morceau is 

 much mutilated, the incisor being bro- 

 ken at its entrance into the alveolus ; 

 its form cannot therefore be precisely 

 given ; but it is evident that it was 



cwrved upwards.' — Stutchbury, Report 

 on the Discovery of Gold in Australia, 

 1855, p. 53. 



3 Phil. Trans., vol. cxlix. p. 318. 



4 Palaeontology, p. 432. 



