264 Professor Pictet on the Distribution of Fossils. 



genera, we likewise find in them true nautili, not differing 

 much from the present species. Thus, along with spirifer 

 and productus, which are no longer found, there lived in 

 these same formations terebratulse, which possess forms 

 closely analogous to those of all the subsequent formations, 

 and of the present epoch. The same thing takes place in 

 regard to the tertiary epoch ; for these same formations 

 which have furnished remarkable extinct genera in the order 

 of pachyderms, likewise produce some bats and small car- 

 nivora, which can scarcely be distinguished from species 

 now living. 



Third Law. — The comparison of the faunas of the different 

 epochs, shews that the temperature on the surface of the earth 

 has undergone variation. The facts on which this law has 

 been established are, that we discover fossil animals in those 

 parts of the globe where they could not live in our own times, 

 on account of the cold ;* and that the faunas of some recent 

 epochs — and, in particular, the tertiary formations of Europe 

 — present more analogy to the animals of the torrid zone 

 than to those of temperate zones. To these zoological con- 

 siderations we have likewise to add the arguments drawn 

 from the vegetable kingdom. During the epoch of the coal 

 formation, Europe has been covered with a rich and large- 

 sized vegetation, of such a kind that it can only be compared 

 to that of certain intertropical countries. 



These facts concur in shewing a difference of temperature ; 

 but it is probable, at the same time, that a too hasty genera- 

 lisation has been made, when it has been concluded that there 

 has been a constant and uniform decrease of temperature. 

 The first-mentioned fact, for example, proves that, during the 

 diluvian epoch, the shores of the Icy Sea have been less cold 

 than they now are ; but it by no means proves that this phe- 

 nomenon has been general over the globe at that period ; 

 neither does it demonstrate that, in the long periods which 

 have preceded, the heat has been still greater. 



* Thus, elephants and rhinoceroses have lived under the latitude of the 

 Icy Sea, where, at the present time, these regions could not furnish the 

 vegetables necessary for their sustenance. 



