178 Scientific hitelligence — Geology. 



facts, and we may already draw from them the general conse- 

 quence that each group of species represents the mean tempera- 

 ture of each of these regions. But there are certain species of 

 more local and others of more general occurrence. Thus, to 

 give an example of the latter, the Buccmum undatum is found 

 from the North Cape to the Senegal, modified according to the 

 temperature ; and it is easy to distinguish the varieties peculiar 

 to the three principal conditions of temperature. Other species, 

 more sensible to the influences of temperature, are much more 

 local, and they are precisely those which it is the most important 

 to know. The following are some of them. The Buccinum 

 glaciate and Cardium Groenlandicum do not extend beyond the 

 polar circle, and are found in Norway and Greenland. The 

 Terehratula psittacea lives between the fifty-fifth and seventy-' 

 fifth degree. In my opinion these species and several others 

 represent the mean temperature of the north of Norway. 

 The Tellina Baltica, Patella 7ioachina, Natica clausa, Pa- 

 tella iestudinalis, several species of the genus Astarte, and 

 some other species, seem to me to represent the mean tempera- 

 ture of the north of England, the south of Sweden, and Den- 

 mark. In the English Channel, on the coasts of France and 

 England, there exist several species peculiar to our temperature, 

 such as the Psammobia vespertina, Pecten irregularis^ &c. The 

 coasts of Spain and Portugal are less known than those of New 

 Holland and North America. Among the large number of 

 species known in the intertropical zone, tlicre are a great many 

 which are peculiar to it, and which, accustomed to a high and 

 little varying chmate, do not occur living in any other part of the 

 surface of the globe ; they express then with fidelity the tempera- 

 ture of the seas in which they live. These facts relative to the 

 coincidence of the temperature with the presence of certain 

 species, necessarily preceded the remarks which I have to make 

 regarding the temperature of the geological epochs of tertiary 

 deposits. I ought to add that, in order to determine this inte- 

 resting question, it was necessary to compare carefully all the 

 known Hving species with all those found in the various tertiary 

 formations of Europe. The following are the principal results 

 obtained by the aid of this long investigation : — 1 . The tertiary 

 formations of Europe do not contain a single species in common 



