THE OI.nEST MAMMALS. 121 



CHAPTER XII, 



THE OLDEST MAMMALS. 



Up to the jear 1818 it was a generally received axiom of 

 geology tliat mammals were totally unknown before the 

 Tertiary period ; and that period was consequently 

 designated the age of mammals — a name, by the way, 

 which is still perfectly approjn'iate, if taken to imply that 

 these animals then, and then only, became the dominant 

 inhabitants of the world. In that year, however, the 

 illustrious Cuvier, during a visit to the museum at Oxford, 

 was shown two minute jaws, carrying a number of cusped 

 teeth, which had been obtained in the neighbouring- 

 quarries of Stonesfield, from the rock known as the 

 ytonesfield slate, belonging to the lower part of the great 

 Jurassic, or Oolitic, system. After careful examination, 

 the French anatomist pronounced confidently that these 

 two tiny little jaws, neither of which exceeded an inch in 

 length, were those of mammals, and he further suggested 

 that they would ];irove to belong to a species of opossum. 

 Although this opinion was given in the year 1818, it does 

 not appear that it was pulilished till the year 1825, when 

 the second edition of the fifth volume of the immortal 

 ■' Ossements Fosiles " saw the light. In pviblishing this 

 epoch-making notice of the occun-ence of mammals in the 

 Secondary period, Cuvier, with the usual caution of 

 naturalists, was careful to add the proviso that everything 

 depended on whetlier the specimens he saw had really 

 been obtained from the Stonesfield slate. Unfortunately, 

 there does not apjieai- to be anj' record stating by whom, 

 or at what date, these original specimens — now forming 

 some of the most valued treasures of the Oxford Museum 

 — were obtained from the Stonesfield slate ; Imt that they 

 did come from that formation is perfectly certain. Indeed,, 

 other specimens have been subsequently obtained from the 

 same beds, showing certain characteristic Stonesfield 



