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III. — Observations on the Fossils representing the Thylacotherium Pre- 

 vostii, Valenciennes, with reference to the Doubts of its Mammalian 

 and Marsupial Nature recently promulgated ; and on the Phascolothe- ' 

 rium Bucklandi. 



By RICHARD OWEN, Esq., F.G.S., F.R.S. 



PART I. — On the Thylacotherium. 



[Read November 21, 1838.] 



Plate V. 



X HE ample experience which Comparative Anatomists possess of the truth and 

 tact with which the illustrious Cuvier formed his judgement of the nature and 

 affinities of an extinct animal from an inspection of part, or even a single frag- 

 ment of its skeleton, would justify our not attaching much weight to a conflicting 

 opinion, maintained on mere theoretical grounds, and without actual inspection of 

 the fossil itself ; but when the accuracy of one of Cuvier's interpretations is called 

 in question by an anatomist so eminent as his successor in the chair of Com- 

 parative Anatomy, the confidence of geologists in their great guide in Palaeon- 

 tology becomes liable to be shaken, and an examination into the validity of such 

 objections is requisite. 



The doubts which M. de Blainville has published*, as to the mammalian nature 

 of the animals represented by the well-known fossil jaws discovered in the Stones- 

 field oolite, rest, — first, on their being probably too imperfect to yield any con- 

 clusive evidence as to the class of animals to which they may have belonged ; and, 

 secondly, on an interpretation of appearances presented by casts of these fossils 

 leading to conclusions opposite to those which Ciivier, and afterwards M. Valen- 

 ciennes, derived from an inspection of the actual fossils. 



It is in compliance chiefly with Dr. Buckland's request that I have undertaken 

 to test the validity of these doubts, for which purpose he has transmitted to me 

 from Oxford the two original fossils, each consisting of the ramus, or lateral half 

 of a lower jaw ; I have also re-examined the similar, but larger and more perfect 



* " Doutes sur le pretendu Didelphe de Stonesfield." Comptes Rendus de I'Acad. de Sciences, Oct. 

 22nd, 1838. 



