founded upon the Study of Fossil Shells. 1 3 



2. Those few of which the corresponding species do not 

 exist in the Mediterranean ; but are found in the Atlantic, in 

 the Red Sea, and in the Indian Ocean. 



3. Those of which the analogous species do not exist at all. 

 These observations led me to think that the Mediterranean 



had undergone a slight lowering of temperature, since the 

 chain of Mount Atlas on one side, and that of the Apennines 

 on the other, had acquired their present elevation. These 

 changes in the elevation of strata, and consequently of tem- 

 perature, would explain the extinction of the recent species 

 analogous to those of the third series, and the particular 

 distribution of species of the second series, in warmer seas 

 than the Mediterranean. This occasions me to consider it as 

 very probable, that, before the latest changes in the borders 

 of this sea, it had a wide communication with the Atlantic, by 

 the Great Desert of Africa ; and another with the Indian 

 Ocean, either by the Red Sea, or by the low lands of Arabia, 

 which separate the Mediterranean from the Persian Gulf. 



Belonging to the second tertiary period are a great number 

 of small basins, scattered particularly about the centre of 

 Europe. La Superga, near Turin, the basin of the Gironde, 

 the crag of Touraine, the little basin of Angers, the basin of 

 Vienna in Austria, Podolia, Wolhynia, and some other traces 

 upon the southern frontier of Russia in Europe, of which 

 some remains show themselves not far from Moscow. The 

 lacustrine strata of Mayence, and on the borders of the Rhine, 

 belong, probably, also to this period. 



During this epoch, the temperature was very different from 

 what it is at present in the places we have just mentioned. 

 Indeed, the species peculiar to Senegal and the Gulf of 

 Guinea, those which best indicate the temperature of that 

 part of the equatorial zone, are found in a fossil state in 

 beds belonging to this second period. 



Now, if, reckoning from the number of species, and the great 

 quantity of individuals belonging to each of them, we calculate 

 where their largest assemblage is to be found, it would be along 

 the basin of the Gironde that we should make the line of the 

 greatest intensity of heat to pass; and we should say, an 

 equatorial temperature has formerly reigned there during a 

 long succession of ages. 



There must have been this temperature, for the species 

 now fossil, to have lived formerly in our seas ; for they in- 

 habit there no longer, and could not do so at the present time. 

 As they once lived there, why should they not live there now, 

 if the temperature had remained the same? 



This temperature must have continued during a long course 



