58 report — 1842. 



The first exception to any generalization which has assumed the cha- 

 racter of a law, is always admitted with difficulty, and by the strict or 

 mechanical systematists with reluctance. The geological arguments by 

 which M. Prevost endeavoured to invalidate the conclusions of Dr. Buck- 

 land, were soon and satisfactorily refuted by Dr. Fitton ; and the question 

 as to the real age of the rock containing the bones in question has not since 

 been agitated. The attempts to remove the supposed anomaly by inter- 

 preting the appearances in the fossils as indications of a cold-blooded spe- 

 cies, have been more frequent and persevering; and they assumed the 

 character of so systematic a refutation of the Cuvierian view, in the me- 

 moirs communicated by M. de Blainville to the French Academy in the 

 year 1838, that a close and thorough re-examination of the fossils in ques- 

 tion became imperatively called for, in order that the doubts cast upon their 

 mammalian nature might be tested. For this purpose the original fossil jaw 

 described by Dr. Buckland, and those subsequently obtained from the 

 Stonesfield slate and preserved in the Oxford Museum, were submitted to 

 my inspection. I carefully examined the specimen described by Mr. Brode- 

 rip and presented by him to the British Museum, and likewise that which is 

 preserved in the Museum of the Philosophical Society at York. The results 

 of these examinations were communicated to the Geological Society, and 

 have been published with new and more exact figures of the fossils in the 

 6th vol., 2nd series, of the Transactions of the Society. 



By a very singular coincidence the mammalian fossils from the Stones- 

 field slate, hitherto determined, are all portions of the loAver jaw ; whether 

 belonging to individuals of different species, or of different genera, or even, 

 as appears by examination of new specimens acquired since the publication 

 of my memoir of 1838, of different orders of Mammalia. 



The first fossil was referred originally to the genus Didelphys, from the 

 resemblance of the grinders to those of the opossums ; but Cuvier expressly 

 states that they exceeded in number the molar series in that or any other known 

 carnivorous genus of mammal. M. Agassiz, originally regarding this fossil as 

 insufficient to determine the nature of the animal to which it belonged, sub- 

 sequently proposed, nevertheless, a generic name, Ampltigonus, for that 

 animal, expressive of its supposed ambiguous nature. M. de Blainville, 

 likewise, though participating in the incertitude or doubt which M. Agassiz 

 had cast upon the original determination of the Stonesfield fossil, had as 

 little hesitation in suggesting a name for the new genus which it seemed to 

 indicate, whatever might subsequently prove to be its characters or affinities ; 

 and it is remarkable that the Greek compound ' Amphitherium,' should 

 imply by its terminal element a relation to the class Mammalia, which the 

 two memoirs read to the French Academy by its inventor were designed to 

 disprove. 



M. Valenciennes, in his reply to M. de Blainville, arriving at the conclu- 

 sion that the fossil jaw described and figured by M. Prevost and Dr. Buck- 

 land not only belonged to a mammalian but likewise to a marsupial animal, 

 proposed for it a third generic name, indicative of these presumed affinities, 

 viz. Thylacotherium. 



The arguments of M. Valenciennes were opposed in a second detailed 

 memoir by M. de Blainville, who concluded by stating that he felt himself 

 compelled to pause, at least until fresh evidence was produced, in the con- 

 viction that the portions of fossil jaws found at Stonesfield, certainly did not 

 belong to a marsupial — probably not to a mammalian genus, either insectivo- 

 rous or amphibious — that, on the contrary, it was most likely the animal had 

 been oviparous, and that, had not M. Agassiz decidedly given his opinion 



