On the Palceontology of South America, 365: 



On the contrary, the Neocomian formation of the Straits of Ma- 

 gellan exhibits analogies with the basin of the Mediterranean. 

 However this may be, the Neocomian seas, with their mollus- 

 cous animals, similar and identical, extended at the same time 

 in the southern hemisphere, as far as the 54°, and in the nor- 

 thern from the 4° to the 48° of latitude, that is to say, to 

 more than 2500 leagues in length, with a breadth of 75 de- 

 grees, or more than 1800 leagues. The laws which direct the 

 actual geographical distribution of living beings upon the sur- 

 face of our planet, always depend upon a complete unifor- 

 mity of the conditions of existence and of temperature. Hence 

 we ought, by comparison, to conclude that the simultaneous 

 presence of the same species in the depths of the Neocomian 

 seas of Columbia, of the Straits of Magellan, and of France, 

 denote for this epoch, an unity of temperature throughout the 

 different localities, which no longer exists at the present time, 

 since Columbia is under the torrid zone, France is relatively a 

 temperate country, and the region of the Straits of Magellan 

 a very cold one. As regards the Silurian and Devonian sys- 

 tems, T have already directed attention to the agency of the 

 central terrestrial heat which probably existed in those early 

 periods in which living beings existed in the world. I have 

 also dwelt upon the same agency, as operating at a later period 

 upon the Carboniferous system. The attention I have di- 

 rected to the Jurassic deposits of Europe has not less satisfied 

 me, by the existence of the Oxford beds, in every way iden- 

 tical, in France and to the north of the Oural Mountains,* 

 that the polar cold did not exist for about a half at least of 

 the Jura period. To this I may now add, that I have reached 

 the same conclusions with respect to the newer cretaceous for- 

 mations. It appears then certain, that, during the Neocomian 

 formation, not only was the terrestrial heat sufficiently strong 

 to counteract the influence of the latitude of the temperate 

 regions, but also completely to annihilate the icy influence of 

 the poles. 



* I have arrived at this curious result by the comparison of the rich fossil re- 

 mains which MM. Murchison and Do Verneuil have discovered in the Jura for- 

 mation of Russia, and which they have entrusted to me for examination and 

 publication. 



VOL. XXXV. NO. LXX. OCTOBER 1843. 2 B 



