378 PALAEONTOLOGY AND EVOLUTION XI 



complete and unmistakable break in the line of 

 biological continuity. 



Among the twelve or fourteen species of Mam- 

 malia which are said to have been found in the 

 Purbecks, not one is a member of the orders 

 Cheiroptera, Rodentia, Ungulata, or Carnivora, 

 which are so well represented in the Tertiaries. 

 No Insectivora are certainly known, nor any 

 opossum-like Marsupials. Thus there is a vast 

 negative difference between the Cainozoic and 

 the Mesozoic mammalian faunaB of Europe. But 

 there is a still more important positive difference, 

 inasmuch as all these Mammalia appear to be 

 Marsupials belonging to Australian groups, and 

 thus appertaining to a different distributional 

 province from the Eocene and Miocene marsupials, 

 which are Austro-Columbian. So far as the im- 

 perfect materials which exist enable a judgment 

 to be formed, the same law appears to have held 

 good for all the earlier Mesozoic Mammalia. Of 

 the Stonesfield slate mammals, one, Amphither- 

 ium, has a definitely Australian character; one, 

 Phascolotherium, may be either Dasyurid or 

 Didelphine ; of a third, Stereognatlius, nothing 

 can at present be said. The two mammals 

 of the Trias, also, appear to belong to Australian 

 groups. 



Every one is aware of the many curious points 

 of resemblance between the marine fauna of the 

 European Mesozoic rocks and that which now 



