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CHAPTER XI. 



. 



CLIMATE OF THE MIOCENE DISTRICT. 



PLANTS and animals were doubtless subjected to the- same laws 

 in former ages as in the present day. Every species now, as in 

 geological times, requires for its development a definite amount 

 of light and heat, of air and water, and its distribution over the 

 surface of the earth is dependent upon these conditions. So 

 much influence has particularly been exerted by heat and water, 

 that, owing to these agencies, each species of the animal as well 

 as the vegetable kingdom has been confined within definite 

 limits. Important information is thus afforded by fossil plants 

 and animals respecting the climate of bygone ages. When a 

 collection of plants is laid before a botanist who is familiar with 

 the geographical divisions of the vegetable world, he will be 

 able to decide on the climate of the country from which the 

 plants are derived. A climatal limitation of area applies also to 

 animals, and particularly insects, which differ greatly in accord- 

 ance with the conditions of climate. If correct inferences can 

 be drawn from existing plants and animals as to the climate of 

 the country to which they belong, accurate conclusions may 

 also be possible with respect to extinct or fossil species ; and our 

 deductions will attain more certainty in proportion to the abun- 

 dance of the materials at our command, and to the near alliance 

 of the animals and plants to those now living. 



A great number of species have been found in the fauna and 

 flora of the Tertiary epoch which are nearly allied to existing 

 forms. Among the inhabitants of the sea the relationship in 

 many cases amounts to a perfect identity of species ; and the ap- 

 proximation between moderns and ancients in many species of 

 land plants and animals is so close that the Tertiary species 



