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Ch. XXXVIII.] ANIMALS OF THE NEOTEOPICAL REGION. 



337 



species were again exterminated, we cannot conjecture. 



World 



It 



means 



in the present state of our knowledge, to wonder at the 

 extinction of any species. A small insect, which lays its 

 eggs in the navels of horses, cattle, and dogs, when first born 

 makes it impossible, says Darwin, for any of these animals 

 to run wild in Paraguay ; * and we are extremely ignorant as 

 to the various animals and plants, on the coexistence of 

 which the well-being of any one species may depend. 



Besides, as geologists, we must remember that the horse 

 tribe and the elephants have been waning groups since the 

 Miocene and Pliocene periods in the northern hemisphere. 

 In northern India alone, the fossil remains of the Sewalik 

 hills have shown us that there were in the Upper Miocene 

 Period no less than seven distinct species of proboscidians of 

 the genera Ele^has, Mastodon, and Stegodon (as defined by 

 Falconer), and besides these several species of mastodon 

 flourished contemporaneously in Europe. There are now only 

 two^ living^ representatives of the whole group, viz. Elephas 



^^-icanus. In like manner no less than twelve 

 equine species referred by Leidy to seven genera, have been 

 already detected in the Pliocene and Post-Pliocene forma 

 tions of the United States, no one of which survived in 



4/^ 



time 



to a great extent peculiar to 



many 



It has been objected that the insect fauna of Chili, although 



.,.^.„x .. , g^^^j^ Temperate America, 



ns of butterflies and beetles' 

 such as CoHas, Carabus and others, which are common to the 

 nortnern hemisphere, and are not found in the intermediate 

 tropical region. These insects, however, may well be sun 

 posed to have passed from north to south along the hic^her 

 region of the Andes, during the cold of the Glacial Period 

 and almost all of them seem to have been so modified in 

 their character, that the allied forms of the north and on 

 are not specifically identical. As to the 



mars 



* Darwin, 'Origin of Species,' 

 edition, p. 83. 



4th Lraska Fossil Eemains, Proc. of Acad 



1 See Leidy and Hayden on Ne- 



Nat. Sci. Pliiladelp. 1858, p. 89. 



VOL. II, 





