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 Conti- 
nent 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 bar- 
riers 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 Craq. 
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 Europe. 
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. Conciusions. 
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 con- 
stant 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.’ 
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