CONCLUSIONS TO BE DRAWN FROM FOSSILS. 75 



formerly believed to be confined to the Arctic Seas have, by 

 reason of the extension of Polar currents, a wide range to 

 the south ; and this has thrown doubt upon the conclusions 

 drawn from fossil shells as to the Arctic conditions under 

 which certain beds were supposed to have been deposited. 



d. The distribution of animals at the present day is 

 certainly dependent upon other conditions beside climate 

 alone ; and the causes which now limit the range of given 

 animals are certainly such as belong to the existing order of 

 things. But the establishment of the present order of things 

 does not date back in many cases to the introduction of the 

 present species of animals. Even in the case, therefore, of 

 existing species of animals, it can often be shown that the 

 past distribution of the species was different formerly to 

 what it is now, not necessarily because the climate has 

 changed, but because of the alteration of other conditions 

 essential to the life of the species or conducing to its ex- 

 tension. 



Still, we are in many cases able to draw completely 

 reliable conclusions as to the climate of a given geological 

 period, by an examination of the fossils belonging to the 

 period. Among the more striking examples of how the past 

 climate of a region may be deduced from the study of the 

 organic remains contained in its rocks, the following may be 

 mentioned : It has been shown that in Eocene times, or at 

 the commencement of the Tertiary period, the climate of 

 what is now Western Europe was of a tropical or sub- 

 tropical character. Thus the Eocene beds are found to 

 contain the remains of shells such as now inhabit tropical 

 seas, as, for example, Cowries and Volutes ; and with these 

 are the fruits of palms, and the remains of other tropical 

 plants. It has been shown, again, that in Miocene times, 

 or about the middle of the Tertiary period, Central Europe 

 was peopled with a luxuriant flora resembling that of the 

 warmer parts of the United States, and leading to the con- 

 clusion that the mean annual temperature must have been 

 at least 30 hotter than it is at present. It has been shown 

 that, at the same time, Greenland, now buried beneath a vast 



