Ti OBSERVATIONS UPON 



but there are ten in a series, a number found in no other car- 

 nassier with which we are acquainted." 



It is impossible to doubt that the expressions "quelque Di- 

 delphe" and "celles des Sarigues" must have been employed 

 to intimate that the fossil animal was a pouched mammal, — 

 in other words that it belonged to the order Marsupialia, 

 Geoffroy, and undoubtedly closely related to the didelphs. — 

 His remark upon the number of molars also shows that he 

 believed even then that this mammal, when farther studied, 

 would be regarded as a distinct genus. 



At any rate, however, this opinion confers great importance 

 on this small relic of a jaw, not more than nine or ten lines 

 in length, because it indicates the presence of terrestrial 

 mammals in rocks of more ancient deposition than the chalk. 



Cuvier having never had these fossil jaws in his own ca- 

 binet, — having been unable to compare them with the skele- 

 tons of existing species which were brought together in his 

 extensive collection of comparative anatomy, but merely hav- 

 ing received the drawing, made by M. Constant Prevost, of 

 the jaw in the Oxford Museum, and also that of a larger but 

 less perfect one, preserved in the Museum of the Rev. C. 

 Sykes, — did not treat of these remains in a special memoir, 

 in which he might have endeavoured to establish their rela- 

 tions with other vertebrated animals. 



From this time, geologists, confiding in the authority and 

 judgment of the great anatomist, have cited the Stonesfield 

 Didelphis as an exception to the generally -received law, that 

 fossil mammals are not to be met with in the beds belonging 

 to the secondary period ; more recently, however, doubts have 

 been raised by naturalists and anatomists, concerning this 

 determination. 



It has been made known that these remains of Vertebrata 

 were regarded as having belonged to the class Reptilia : this 

 opinion is said to have originated with Professor Grant, in 

 the German translation of Dr. Buckland's Bridgewater Trea- 

 tise, by M. Agassiz 



If this new determination could have been applied without 

 contradiction to the half jaw examined by Cuvier, it would 

 have had the advantage of restoring to the order of hitherto- 

 observed phenomena, the nature of the animals from the 

 Stonesfield beds ; but M. de Blainville has again rendered 

 the opinion uncertain, in the elaborate memoir lately read by 

 him before the Academy, and published in the eighth num- 

 ber of the ' Comptes Rendus' for 1838, 2 under the title of 



2 For a translation ofM. de Blainville's Memoir, see 'Mag. Nat. Hist.' 

 1838, p. 639.-^7. 



