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Show 395 I N S 'r R U C 'r I 0 N S 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 I, 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 habitations of the living species, are also givet1. No allusion is made to any secondary fossil shells; the word fossil, therefore, must always be understoorl 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 follows:- Lhlng Species. Univalves • 3,616 Bivalves • 1,164 4,780 Fossil Species. • 2,098 I 938 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, hut are mentioned as being common to more than one tertiary ve1iod; 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 |