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Show 39G INSTRUCTIONS FOR USING period. Thus the number of fossil species named in the tables amounts to 782, consisting of- Species found both living and fossil 426 Species fossil only, but common to more than one tertiary period 123 Species fossil only, and named merely as found in two or more formations of the same period 233 782 A few will be found without specific names, because they have not yet been described or named by any authors. The tables are continuous from p. 2 top. 45, and the description of each species extends across two pages. The following examples will best illustrate the object of the tables. If we take the first genus, Aspergillum (p. 2), we find that- Column 1 gives the name of the genus. " " 2 shows that four living species of the genus are l\nown to M. Deshayes. 3 that he has seen one fossil species. 4 is left blank, because the single fossil species has not yet been identified with any living species. 5 is also blanl{, because the fossil species is only known in one period or formation. 6 is also blank, because the fossil species not having been identified with a living species, it was unnecessary to mention the habitation of any of the four living species. The columns of the three periods are left blank, because the fossil species has not been found in more than one period. In the column of localities on the right of the right-hand page, in the subdivision headed Bordeaux, the figure 1 denotes that one species of fossil Aspergillum has been found in that locality. To select another example: if we take the genus Solen (p. 2), we find that- Column 2 shows that twenty-six living species of the genus are known to M. Deshayes. " 3 that he has seen nineteen fossil species of the genus. M. DESIIAYES's TABLES OF SIIELLS. 397 Column 4 gives the name of the species Solen vagina, because that species is found both living and fossil. , 5 is left blank, because the names of those species only are placed in this column which have no living analocrues t:> ' but are found in more than one period, or in more than one f01·mation of the same period. [Thus, in the next line, Solen siliquarius has no living analogue, but it occurs in two formations of the Miocene period, viz. at Bordeaux and in Touraine.] , 6 shows that the living species of Solen vagina inhabits the European Ocean and Mediterranean. , The two asterisks in the column of the Pliocene period show that the species is found in two formations of that period, viz. in the Subapennine hills and the English Cl'ag. The asterisk in the column of the Miocene period shows that this species is found in the basin of Vienna. The word Baden in the next column indicates that the species is also fount! fossil in that locality. The column of the Eocene period is blank, because the shell has not been found in any formation belonging to that period. The figures in the column of localities will be understood by what we said above. In summing up these figures it will be found that they amount to thirty-one, whereas it is stated, in the third column of the leftl: and page, that only nineteen fossil species have been found. The disagreement arises from this-that the same species occur in more than one locality, and thus come to be counted more than once in the column of localities. N.B. In some cases, before the totals of the species in the columns of localities can tally with the figures in the third column, the species enumeratetl in the supplementary table of localities, p. 46, must be taken into account. A note of interrogation ndued to the asterisk (*?) indicates a doubt as to the correct identification of the shell, either because the shell is a variety which has a. somewhat distant analogy to the recognized type of |