174 



MEANING OF THE SYSTEM. 



eocene Ungulates (Pachydermata). In the same locality are found 

 the well preserved remains of the bones of peculiar Carnivora which 

 are well worthy of remark. These are the Hysenodonta. It was for 

 a long time doubtful whether they were Marsupials or not, until 

 Filhol showed from the reserve teeth of their permanent dentition 

 that they were probably of the nature of placental Carnivora. The 

 great agreement of the molars of these Hysenodonta with those of 



the carnivorous Mar- 

 supials, as well as the 

 small size of the skull 

 cavity and the rela- 

 tively slight develop- 

 ment of the brain, 

 support the view, 

 which is also rendered 

 probable by many 

 other circumstances, 

 that placental Mam- 

 malia have developed 

 from the Marsupials 

 of the ruesozoic 

 period. 



In the oldest strata 

 of the Eocene forma- 

 tions in both hemi- 

 spheres, the higher 

 placental Mammalia 

 already appear in a 

 rich variety of forms, 

 which contrast mark- 

 edly with one another 

 (Artiodacti/la, Peris- 

 sodactyla}. There is, 

 however, no ground 



for regarding the immeasurable period from the oldest Eocene to the 

 Keuper, in which the oldest Mammalian remains (the teeth and 

 bones of insectivorous Marsupials) have been found, as the period in 

 which this higher development of the Mammalian organism has been 

 effected. 



In other cases also the science of palaeontology has led to the 

 discovery of intermediate forms between groups and even between 



PIG. 



118. Pferodactylus crasxiroxtrig (after Goldfuss) about 

 one-third natural size. 



