1869.] DUNCAN—CORAL FAUNAS OF WESTERN EUROPE. 69 
group of islands, receives additional force from the study of the suc- 
cessive reef-areas of the Nummulitic, Oligocene, and Miocene periods. 
The first of these contained a coral fauna which was as representative 
of that of the Cretaceous reefs as this was of the Oolitic; and thus 
there is another example of the remarkable return of closely allied 
forms to the same area after great alterations in its physical geo- 
graphy had occurred. The Oligocene and Miocene reefs were the 
last on the European area; and the present deep-sea coral fauna 
of the Mediterranean, North Sea, and north-eastern Atlantic is re- 
presentative of the deep-sea coral fauna of the White Chalk. 
The alliances between the consecutive coral faunas which were 
separated by deposits containing the evidences of conditions most 
unfavourable to coral-life indicate that there has been an unbroken 
series of reef-areas within the scope of the emigration of Madrepo- 
rarian ova ever since the Trias. Sometimes the reef-bearing seas 
were on the European area; and then it probably resembled, in its 
geography and natural history, a modern coral-sea. At others the 
physical conditions which characterize the existing state of things 
prevailed ; and then the coral-tracts were remote, and either deep-sea 
forms existed or none at all. Doubtless the continental land was 
very persistent in Northern Europe, and the Arctic sea was shut out 
until the termination of the Mid-tertiary age. ‘The land probably 
often encroached upon the coral tracts, and determined their partial 
or entire destruction. 
Its influence may have been like that of the American continent 
upon the Caribbean Sea. During the Miocene, Trinidad was a vast 
reef, hung on to the older Parian hills, which were submerged and 
far away from land, and it was one of a series. But as the South- 
American coast uprose and the drainage of the new continent was 
poured out through the valley of the Orinoco, so great a mass of fresh 
water and muddy sediment contaminated the Trinitatian area, that 
hardly any corals grew around its old reefs after they they had been 
upheaved in common with the Miocene deposits of the Caribbean 
Sea. A short distance to the north, however, the new coral fauna 
encircles the old. 
Discussion. 
Prof. AtnxanpER Acasstz accounted for the circumscribed area of 
many corals in the Atlantic from the young of many coral species 
attaching themselves within a few hours of their becoming pelagic. 
He traced to the great equatorial current which must have traversed 
the Isthmus of Panama and the Sahara in a precretaceous period 
the distribution of certain forms, which the rising of the Isthmus 
of Panama eventually checked. He mentioned the formation of 
a reef at the present time off the coast of Florida, which threw light 
on the manner in which mudflats were formed, and the sea eventually 
filled. 
Mr. Gwrn Jerrreys objected to the term ‘deep sea” being ap- 
plied to a depth of 10 fathoms only, when the tide in some places 
tose to that extent, and the laminarian zone extended to 15. He 
