66 _ PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 24, 
that now occupy definite positions in the reefs of the Indo-Pacific. 
Even the great reef-making genera Millepora, Porites, Alveopora, 
Madrepora, and Heliastrea are represented in the Eocene reefs by 
numerous species. The number of species in the old reefs quite 
equals that in the existing ones. The stragglers from the reefs which 
formed a part of the British Eocene coral fauna are of the genera 
Stereopsammia, Dendracs, Porites, Litharea, and Axopora. These 
forms, associated as they are with the Dendrophyllie, would not be 
out of place in such an area as the sea-bottom to the south of China, 
or the Gulf of Mexico. 
Great variations of depth occurred in these coral areas; for deep 
sediments containing Nummulites overlie the reefs either directly or 
by inference, and there is a profound flysch superior to the Ober- 
burg, but not in the same district. The Nummulites appear to have 
favoured the reef-areas. 
Oligocene. 
The coralliferous deposit at Brockenhurst, in Hampshire, rests 
upon a freshwater formation which is the equivalent of the fresh- 
water beds of the Lower Headon series. The species of corals are of 
genera which now characterize reefs, and the most prominent are 
Madrepora and Solenastrea. The mollusca associated with the corals 
are identical, for the most part, with those which are found in the 
Oligocene strata of Tongres, Magdeburg, and Latdorf; and they be- 
long to a well-characterized horizon between the Nummulitic and the 
Faluns. The corals of the three localities just mentioned are deep- 
sea and littoral forms more or less under the influence of a reef; but 
the true reefs were in Hampshire and in the Castel-Gomberto dis- 
trict, where they can still be recognized in great masses. 
These reefs contain no less than 50 genera of corals ; and there are 
many species there which are found in the Nummulitic and Miocene 
reefs associated with characteristic forms. The Oligocene reefs dif- 
fered, in species, about as much from those which immediately pre- 
ceded and followed them as the existing West-Indian reefs do from 
those of the Pacific and South Sea. 
The relation of the Oligocene reefs to certain great bathyme- 
trical changes is obvious ; and the Brockenhurst reef was loeated 
upon an area which had been upheaved after the Barton deposits had 
been completed and again slightly depressed. The deep water in 
the German area covered extensive Brown-coal strata. 
The reef-corals began to diminish in the number of their species 
after this time; and the Miocene reefs formed in south-western 
France, northern Italy, Austria, Hungary, Spain, and Malta, do not 
present so varied an assemblage as those of the two preceding forma- 
tions. The oscillations of the south-western area of Europe were 
very great between the Oligocene and the Miocene; and during this 
age reefs and barriers were associated with considerable land-sur- 
faces, and with very variable conditions of sea-bottom. The partial 
upheaval of the Alps (which had been a reef-supporting series of 
hills for two periods) into mountain-ridges, and the general volcanic 
