Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/240

126 chance of any observer adding to his list without being able to devote very much more time to the subject than I have had at my disposal. There is certainly no formation in England, and probably none abroad, the fossils of which have been the object of researches more assiduous and more conscientiously made than those of Mr. Searles Wood. Not only has Mr. Wood formed collections rarely equalled in their completeness and extent, but he has also ably described and illustrated them in the early volumes of the Palaeontographical Society*. The other organic remains of the Crag have also been described in the same work by most competent authorities in the different natural-history sections in the following order:—

Mollusca, by Mr. Searles Wood (Palaeontographical  Society's Monographs†) 1848, 1850, 1856 Corals, by MM. Milne-Edwards and J. Haime.. 1850 Cirripedia, by Mr. Darwin 1851, 1854 Brachiopoda, by Mr. Davidson 1852 Echinodermata, by Mr. Edward Forbes 1852 Entomostraca, by Mr. Rupert Jones 1856 Polyzoa (Bryozoa), by Mr. Busk 1859 Foraminifera, by Messrs. Jones and Parker 1866

We are thus, with the exception of the Mammalia, which are only of recent discovery in the Coralline Crag, furnished with a very complete exposition of the fauna of this formation; but there is still work to be done in defining more exactly, by careful collections on the spot, the fossils of each particular zone. In zones d and f this has been partly done. Zone c is typified at Ramsholt, and may be characterized by its Echinoderms and various large Testacea (see list), as zone e is by its profusion of Bryozoa.

Mollusca.—So large a proportion of the shells of the Crag are of recent species that we are furnished with unusually good data for investigating the conditions under which this deposit was formed, by the study of the geographical range and distribution of those living species, and of the zones and depths through which they range. The tendency of natural history at present is rather to extend and remove the barriers of special zoological provinces. Mr. Gwyn Jeffreys remarks‡:—"It seems to me, after a long and careful study of the question, that no more than two groups (which are apparently distinct from each other) can be recognized in a geographical point of view; and for these I would suggest the general but not inappropriate names of 'Northern' or 'North-European,' and 'Southern' or 'South-European.'" And he adds that"it is extremely difficult to fix the limits of even those comparative areas of distribution; but the 'facies' of each group is manifest to some extent in the littoral or shallow-water species." To these groups, or divisions, Mr. Jeffreys adds a third, viz.

to his original work.
 * I am happy to hear from Mr. Wood that he is engaged upon a supplement

† Last year (1870) the first part of Prof. Owen's 'Fossil Cetacea of the Red Crag' was added to this series.

‡ British Conchology, i. introd. p. lxxxvi.