462 FOSSIL INVERTEBRATED ANIMALS. 



greater than it has been at any other era, if we consider that 

 our era, geologically speaking, is one single period, while the 

 fossil remains are the product of many successive ages. 



The ammonites being met with in Europe, in America, in 

 India, and, according to M. Lamarck, in all countries, exhibit 

 a genus which has been able to exist under all climates, if 

 climates were distributed over the earth in the same manner 

 formerly as they are at present ; or, on the contrary supposi- 

 tion, the universality of this genus would lead us to believe 

 that, throughout the whole earth, the temperature was the same, 

 or that it has undergone a series of successive alterations. 



The nautili and spirulge, being, among existing genera, those 

 which have most affinity with the ammonites, and living only 

 in climates the temperature of which is very elevated, we may 

 believe that in which the ammonites lived was similar. If the 

 presence of the ammonites, in the polar regions, could make us 

 believe that in them the temperature was elevated to the degree 

 in which it is at present in the equatorial regions — as we see 

 no reason why the temperature of the latter might not have 

 been augmented, as it is now, in a relative proportion to the 

 entire quantity of heat over the globe — it will follow, by a ne- 

 cessary consequence, that the intertropical parts of the world 

 must have been uninhabitable. 



If such was the case in the first age of the world, and that 

 subsequently the globe became cooler, life must then have 

 commenced in the polar regions ; and if the globe became 

 more and more refrigerated with the progress of time, those 

 regions must have been the first to become deserted. With 

 this theory many facts accord ; and it has the additional advan- 

 tage of coinciding with the doctrine of those learned theologians 

 who have fixed the site of the garden of Eden exactly at the 

 north pole. 



Certain it is, that the presence, in the northern countries, of 

 the remains of animals and vegetables which, in consequence 

 of the cold, could not exist there now, lends some foundation 



