1869.] DUNCAN—CORAL FAUNAS OF WESTERN EUROPE. 67
phenomena of the Rhine provinces and central France, depended
upon secular operations which were also elevating the whole Continent
and producing rivers and sediments, and they rendered coral-life
at first difficult and then impossible. The deep sea of the period was
in the North Atlantic, and the reefs went round the globe like a belt.
The Maltese reefs felt the warm currents of the area now occupied
by the Sahara; and the reefs of Asia Minor and of the west of Arabia
on the east, with the coral-tracts of the Isthmus of Panama on the
west, opened the main oceans of the globe in one continuous track
of island, atoll, and lagoon. The duration of the Mid-tertiary age,
or of the period which commenced after the destruction of the Castel-
Gomberto reefs, and ended with the grandest upheavals of the highest
mountain masses in the world and the destruction of the Arctic barriers
of Forbes and Austen*, was immense; nevertheless the old and
oft-repeated scheme of reef-formation and grouping of genera and
species prevailed through it, and left its impress upon the present
coral-tracts of the Caribbean and the Indo-Pacific areas.
The Crag.
The littoral and deep-water species of corals found in the Crag are either identical with, or are very closely allied to forms now existing in the British seas and the Atlantic off the western coast of Purope. The Pliocene deposits of the sub-Appenines and Sicily and those of Malaga contain species closely resembling, and some identical with, those of the deep water of the Mediterranean, and some found in the greatest depths of the seas to the west of Europe. There were no reefs on the European area, and the Belgian Crag tells the same story as ours. The reefs were where they now are. There was probably very little difference between the general cha- racteristics of the seas of North-west Europe during the Crag-time and the present.
XI. Conclusions.
The oldest Mesozoic reefs appear to have been formed upon the same plan as those which succeeded them through the consecutive geological ages; and all had the same general grouping of families, genera, and shapes which prevails in every modern reef. The scheme, which was feebly represented in the oldest reefs, became more fully developed in the Oolitic period, and was as perfect during the Nummulitic age as it is now. The faunas of the consecutive reefs rarely had species in common, but the genera were most constant and persistent. Certain coral-shapes and methods of growth and of reproduction prevailed during the whole of the periods; and there is a fair inference to be drawn that the external physical conditions which now are absolutely necessary for the formation and persistence of great aggregations of corals were present during the Mesozoic and Cainozoic periods.
These physical conditions have a geographical importance; and
- Forbes and Austen 'Phys. Geog. Europ. Seas.'
F 2
