ISO THE EVOLUTION OF MAN. 



lower jaws, no fragment of the rest of their bodies having 

 been reserved. According to the logic usually applied to 

 palaeontology by the " exact " opponents of the theory of 

 evolution, the inference drawn from this fact would be 

 that these Mammals had no bones except lower jaws. The 

 remarkable circumstance is, after all, very easily accounted 

 for. The lower jaw of Mammals being a solid and excep- 

 tionally hard bone, but very loosely attached to the skull, it 

 is easily detached from the carcase as the latter is carried 

 down by some river, and, falling to the bottom, is retained 

 in the mud. The rest of the carcase is carried on further, 

 and is gradually destroyed. As all the mammalian lower 

 jaws found, in England, in the Jurassic strata of Stonesfield 

 and Purbeck, exhibit this peculiar process characteristic of 

 the Pouched Animals (Marsupialia), we may infer, from 

 this paheontological fact, that they belonged to Marsupials. 

 No Placental Animals appear to have existed during the 

 Mesolithic Epoch. At least no fossil remains, undoubtedly 

 belonging to these and dating from that epoch, are known. 



The extant Pouched Animals, the most generally knoAvn 

 of which are the gramnivorous Kangaroos and the carni- 

 vorous Pouched Rats, display very considerable difference in 

 their organization, in the form of their bodies and in size, 

 and in many respects correspond to the several orders of 

 Placental Animals. The great majority of them live in 

 Australia, in New Holland, and in a few of the Australian 

 and South Asiatic islands; some few species occur in 

 America. On the other hand, there is no longer a single 

 indio'enous Pouched Animal on the continents of Asia, of 

 Africa, or of Europe. The case was very different during the 

 Mesolithic, and also during the earlier CrenoUthic Epochs 



