242 



THE WORLD OF LIFE 



CHAP. 



skeleton the lower jaw exhibits the usual inflexion of the 

 angle ; and the pelvis carries marsupial bones. A small 

 pouch is present in the female." These small marsupials 

 have been named Caenolestes, while their fossil allies are so 

 numerous and varied that they have to be classed in three 

 families — Abderitidae, Epanorthidae, and Garzoniidae. This 

 is only mentioned here to show the large quantity of 

 materials upon which these conclusions are founded. 



Teachings of Pleistocene Mammalia 



For the purpose of the present work it is not necessary 

 to go into further details as to the development of the 

 higher forms of life, except to call attention to some other 

 cases of the sudden dying out of great numbers of the more 

 developed species or groups during the most recent geological 

 period — the Pleistocene. 



It has already been shown how, in temperate South 

 America, the huge sloths and armadillos, the giant llamas, 

 the strange Toxodontia, and the early forms of horses all 

 disappeared at a comparatively recent epoch. In North 

 America a similar phenomenon occurred. Two extinct lions ; 

 a number of racoons and allied forms, including several 

 extinct genera ; six extinct species of horses ; two tapirs ; two 

 genera of peccaries ; a llama and a camel ; several extinct 

 bisons, sheep, and deer ; two elephants and two mastodons, 

 and four genera of the wonderful terrestrial sloths, ranged 

 over the whole country as far north as Oregon and the Great 

 Lakes in quite recent times ; while four genera of the great 

 ground-sloths have been found as far north as Pennsylvania. 



This remarkable assemblage of large Mammalia at a 

 period so recent as to be coeval with that of man, is most 

 extraordinary ; while that the whole series should have 

 disappeared before historical times is considered by most 

 geologists to be almost mysterious. At an earlier period, 

 especially during the Miocene (Middle Tertiary), North 

 America was also wonderfully rich in Mammalia, including 

 not only the ancestors of existing types, but many now 

 quite extinct. At this time there were several kinds of 

 monkeys allied to South American forms ; numerous extinct 

 Carnivora, including the great sabre-toothed tiger, Machaero- 



