396 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 to p. 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 known 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 blank, 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. 



