forms which are now confined chiefly to the Scandinavian or Arctic provinces. These appear from the commencement of the Crag period. Of the exact ratio in which these forms may have increased during that period we are yet ignorant.
The relation which the Coralline Crag bears to the Crags of Antwerp has been the subject of much inquiry. It was first treated in a systematic manner by Sir Charles Lyell, and his conclusions still generally hold good. The corrected lists and more exact divisions of the several members of the Antwerp Crag, recently given by Prof. G. Dewalque, have, however, rendered some modification necessary.
Taking the Belgian beds in descending order, the relation which their molluscan remains show to those of the Coralline Crag is as under:—
| No. of species of Mollusca in the Antwerp beds. | No. common to the Antwerp beds andthe Coralline Crag. | Proportion of Coralline Crag Species. | ||||
| Scaldisien | Sables jaunes | 197 | 135 | 69 | per cent. | |
| Sables gris | 187 | 133 | 71 | per cent.„ | ||
| Diestien | Sables noirs | 228 | 98 | 43 | per cent.„ | |
This question will be treated more fully in the next part of this paper, in connexion with the Red Crag.
With the Pliocene beds of Monte Mario the Coralline Crag has 147 species in common.
P.S. Owing to the great additions made to the number of known species, and the recognition amongst them of so many Crag species in the recent deep-sea dredgings, the Council of the Society have kindly allowed me to bring the lists of fossils up to the present date (April 1871).
List of the Mollusca found in the Coralline Crag.
This List (alphabetically arranged) is compiled from the Monograph of Mr. Searles Wood, with the addition of Mr. Davidson's Brachiopods, whose references and names of species are given in columns I. and II. Mr. Jeffreys has, with the assistance of Mr. Bell, made some additions to the list of species; these have the letter J prefixed to them in column I. The names to which a¶ is prefixed denote species which Mr. Jeffreys identifies with those now living, in addition to all the species which had been already recognized by Mr. Wood to be living[1]. Every form regarded by Mr. Jeffreys as a variety ranges through all the columns in italics.
Column III. comprises the names adopted by Mr. Jeffreys, except those to which a¶ is prefixed, which he regards as synonyms, or names of later date, but desirable to notice. In this column also are added other names adopted by M. Nyst for the Belgian Crags; the last are within brackets.
Columns IV. and V. indicate the zones of depth or bathymetrical range, and the geographical distribution, both of which have been furnished by Mr. Jeffreys.
- ↑ A very few species, to the names of which a † is prefixed, are not the species to which Mr. Wood referred the Crag fossils, although the latter are living. These are Bulla Lajonkaireana, Eulima subulata, Odostomia truncatula, Rissoa costulata, and Trophon gracile.—J. G. J.
