PRINCIPLES OF GEOLOGY -- VOLUME 3

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 habitations 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 follows:-

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 period; 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 period. Thus the number of fossil species named in the tables amounts to 782, consisting of --

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.

Column 2 shows that four living species of the genus are known to M. Deshayes.

Column 3 that he has seen one fossil species.

Column 4 is left blank, because the single fossil species has not yet been identified with any living species.

Column 5 is also blank, because the fossil species is only known in one period or formation.

Column 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.

Column 3 that he has seen nineteen fossil species of the genus.

Column 4 gives the name of the species Solen vagina, because that species is found both living and fossil.

Column 5 is left blank, because the names of those species only are placed in this column which have no living analogues, but are found in more than one period, or in more than on formation 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.]

Column 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 crag.

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 found 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 left-hand 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 enumerated in the supplementary table of localities, p. 46, must be taken into account.

A note of interrogation added 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 the species, or because the specimen examined was in rather an imperfect state.

The specific names of the tertiary fossil shells which have been found by M. Deshayes to belong to one period only, and for which he has not yet discovered any living analogues, are not given, as their enumeration would have required more space than could be allotted to such a subject in a treatise on Geology; but their aggregate number is included in the subdivisions of the column in the right-hand page headed No. of species in each genus in the following localities,' and in the supplementary table, p.46.

APPENDIX I.

TABLES OF FOSSIL SHELLS, BY MONS^R G. P. DESHAYES, Member of the Geological Society of Paris, &c.

N.B. For a full explanation of the object of these Tables, and instructions as to the manner of using them, see the preceding four pages.

SUPPLEMENTARY TABLE

Containing Localities for which there was not sufficient space in the preceding tables.

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