395 



INSTRUCTIONS 



FOR USING 



M. DESHAYES'S TABLES OF SHELLS, 



APPENDIX I. 



THE object of these Tables is to give a list, not of the characteristic 

 shells of the different tertiary formations, of which some figures are 

 given in plates 1, 2, and 3, but to show the connexion of different periods 

 by indicating the shells common to two or more periods, or common to 

 some tertiary period and to the recent epoch. 



The names also of a considerable number of species are given, as being 

 found common to two or more formations of the same tertiary period. 

 The localities where the fossil species are met with, and the known ha- 

 bitations of the living species, are also given. 



No allusion is made to any secondary fossil shells ; the word fossil, 

 therefore, must always be understood to refer to tertiary formations. 



The number of species of recent and fossil shells which were examined 

 and compared in constructing these tables amounted to 7,816, as fol- 

 lows : 



Living Species. Fossil Species. 



Univalves .3,616 . . . . 2,098 

 Bivalves . 1,164 .... 938 



4,780 3,036 



Of these 3,036 fossil species, 426 were identified with individuals found 

 among the 4,780 living species; 123 of them are only known in a fossil 

 state, but are mentioned as being common to more than one tertiary 

 veriod ; and 233 are enumerated by name, although not common to two 

 tertiary periods, or to some tertiary period and the recent epoch, merely 

 because they have been found in two or more formations of the same 



