On the Fossil Shells of the Paris Basin, 215 



1. Pholas callosa. 



2. Psamobia vespertina, 



3. Pecten irregularis, etc. 



The coasts of Spain and Portugal are less known than 

 those of New Holland or South America. 



The Mediterranean contains also a great number of species 

 peculiar to it ; but as this is an inland sea, we will not now 

 speak of it, lest we should attribute the presence of its 

 species to peculiar circumstances. 



The observations are few in number on the coasts of Africa, 

 from Barbary to Senegal ; but for this important region, we 

 have the excellent work of Adanson, and the commercial 

 relations with Senegal and Guinea have long since enriched 

 the collections of marine shells from this quarter. 



Amidst the great number of species known in the inter- 

 tropical zone, there are many which are peculiar to it, but 

 the list is too long to enter into the particulars in this 

 place. The species inhabiting warm climates are less vari- 

 able, nor are they met with living on any other part of the 

 surface of the globe ; they determine therefore with fidelity 

 the temperature of the sea they inhabit. 



These facts are mentioned as concisely as possible, that 

 they may precede what we have to say on the tempera- 

 ture of the geological epochs of the tertiary strata ; but to 

 afford a solution of this interesting question, it was necessary 

 that the whole of the living species with which we are ac- 

 quainted, should be compared with patience, care, and mi- 

 nuteness, with all those that are found in the different terti- 

 ary beds of Europe ; and here are the principal results 

 obtained by our labours on this subject : — 



1. The tertiary beds of Europe do not contain any one 

 species identical with those of the secondary rocks. 



2. The tertiary beds alone contain species still living. 



3. The analogues of living species are more numerous 

 in proportion as the bed is more recent, and vice versa. 



