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 
