212 On the Fossil Shells of the Paris Basin. 



the environs of Gap ; belong also to the formations of the 

 Paris basin, because they contain the same fossils. It ap- 

 pears, indeed, that the same fossils are presented again 

 in Hungary and in Moldavia, which announces that the 

 sea from which they have been deposited, was vast and 

 extensive. We may remark, from the observations of others, 

 that traces of the presence of the same sea will be found 

 far more extensive than those we have mentioned. A very 

 important question suggests itself here, as depending on a 

 more careful examination of fossil species ; many persons for 

 instance, have been employed in researches relative to the 

 temperature of the earth during the great geological epochs- 

 To arrive at the solution of this question, numerous important 

 things require to be considered, and whatever light we are 

 to hope for on the subject, we believe must result from an 

 investigation of the tertiary beds of Europe, among which 

 those of the Paris basin occupy a principal place ; for the 

 question of temperature is inseparably connected with the 

 character of the animals, whose remains are entombed in these 

 strata. And here we have to encounter the only source of 

 difficulty ; but when the whole of the phenomena connected 

 with the tertiary strata are examined together, they lend a 

 mutual support to the results. We are now accordingly to 

 afford a brief statement of our opinions on the subject, and 

 of the means by which we have formed our conclusions. 



If the character of the plants, as learnedly established by 

 M. Arago, in V Anuaire du Bureau des Longitudes de 1834, 

 enable us to afford an approximation to the mean tempera- 

 ture of periods in which they lived ; if the existence in 

 certain places of the vine, palms, &c. be equivalent with the 

 philosopher to thermometric observations, we thus know 

 that the animals, and above all, those which people the 

 waters of the sea, enable us by their presence to deter- 

 mine very nearly the mean temperature of the places they 

 inhabit. 



