founded upon the Study of Fossil Shells. 1 1 



Tellma baltica, Patella Noachina, Natica clausa, Patella 

 testudinalis, with many species of the genus Astarte, and 

 numerous others, represent, to me, the mean temperature 

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

 mark. 



In the Channel, upon the coasts of France and England, 

 there exist, also, many species peculiar to our climate : — 1 . 

 Psammobia vespertina, 2. Pecten irregularis, &c. 



The shores of Spain and Portugal are more unknown than 

 those of New Holland or South America. 



The Mediterranean contains, also, a great number of species 

 which are peculiar to itself; but, as they belong to an inland 

 sea, I will not speak of them at present, lest their occurrence 

 should be attributed to this particular and exceptionable cir- 

 cumstance. 



But few observations have been made upon the coasts of 

 Africa, from Barbary to Senegal; though for this important 

 region we have the excellent work of Adanson ; and the fre- 

 quent intercourse, in the way of commerce, with Senegal and 

 Guinea, has long enriched our collections with the marine 

 shells of that part of the world. Among the great number of 

 known species in the torrid zone, there are many which are 

 peculiar to it. The list of them is too long to be given here. 

 These species, habituated to a climate which has little varia- 

 tion, are not found in a recent state upon any other point on 

 the surface of the globe ; they therefore denote exactly the 

 temperature of the seas they inhabit. 



These facts demand, without doubt, to be developed in a 

 work expressly for that purpose : they lead me to hope that 

 zoologists will be able eventually to reply to questions such 

 as this : — "A series of species being given, to point out the 

 climate of the spot from which they have been procured." 

 It is thus that, in a period not far distant, I venture to hope 

 that the attention of zoologists, directed towards a new end, 

 will give to their science the means of confirming, and some- 

 times filling up what is deficient in, the experience of the 

 natural philosopher. 



These facts relating to the coincidence of temperature with 

 the presence of certain species, mentioned with the greatest 

 possible conciseness, ought to precede what I have to say 

 upon the temperature of the geological epochs of the tertiary 

 strata. I should add, that, to arrive at this interesting ques- 

 tion, it is necessary to compare, with care and patient minute- 

 ness, all the known species of recent shells with all those 

 which are brought from the tertiary strata of Europe. The 



