Mr. Owen on the Phascolotherium. 59 



Still I must repeat, that the jaws of the Thylacothere, as at present known, resemble 

 those of the small Opossums more closely than any other group of the mammi- 

 ferous class ; and in the number of the teeth, the Australian genus Myrmecobius 

 offers the nearest approach to them. 



It is, however, comparatively of little consequence to what particular order of 

 Mammals the Stonesfield jaws belong, provided it can be certainly proved from 

 them that they do belong to the class Mammalia. 



The announcement of the fact of mammiferous remains in the oolitic formations, 

 as it invalidated a received and general proposition relative to the first appearance 

 of these remains in the component strata of the earth's crust, gave rise, in the 

 minds of those philosophers who were unwilling to modify the general law so as 

 to include the new fact, in the first place to doubts as to the antiquity of the ma- 

 trix ; and afterwards, when these doubts could no longer be maintained, to a denial 

 of the high organization of the fossils. 



With respect to the fossils themselves it is asserted, — 



1st. That they are too imperfect to support any safe conclusion as to the class 

 of Vertebrates to which they belonged ; and that therefore, since all previous ex- 

 perience is contrary to the existence of mammiferous remains below the chalk or 

 anterior to the Eocene period, the cold-blooded Ovipara ought to have the benefit 

 of the doubt, and the fossils in question should be transferred to their low organized 

 community. 



The answer to this objection, which is founded on a view of casts only, is simply 

 an appeal to the fossils themselves ; the result of which has already been given as 

 regards the Thylacotherium. 



2nd. These natural hieroglyphics, though considerably time-worn, being allowed 

 to be sufficiently entire to give, if rightly interpreted, the date of the strata on 

 which they are inscribed, we have to consider the differences of opinion as to 

 their real form and meaning. In other words, the objections to the mammiferous 

 nature of the Stonesfield jaws rest not only on a difference of opinion as to their 

 actual structure, but also on a different interpretation of admitted appearances. 



It is asserted that the jaws in question must belong to the cold-blooded Verte- 

 brates, because the articular surface is in the form of an entering angle. My an- 

 swer to this has been, that the articular surface is supported on a prominence, and 

 that that prominence is convex ; and that a convex condyle is met with in no 

 other class of Vertebrata, save in the Mammalia. 



It is asserted, again, that the teeth are all of an uniform structure, as in certain 

 reptiles. But this argument, in like manner, falls to the ground on reference to 

 the fossils themselves ; the contrary being the fact, and the actual structure of the 

 teeth strongly supporting the mammiferous theory of the fossils. 



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