54 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 24,
the littoral corals. The peculiarities of reef, lagoon, and shallow-water
species, and the relations of the two faunas to each other
are then explained. The exceptional species are considered, and a
typical list of genera whose species form existing reefs and contributed
to those of the past is given. The representatives of some of
the modern genera in old reefs are noticed, and then the essential
principles of the line of argument are stated. For instance the correspondency
of physical conditions during the deposition of strata
containing analogous forms, the presence of compound coenenchymal
species indicating neighbouring reefs, and their absence in places
where simple or non-coenenchymal Madreporaria are found, being
characteristic of deep-sea areas which were remote from coral-seas.
The physical conditions of the seas of Western Europe from the
Trias to the present time are considered, and the geographical peculiarities
now witnessed in association with reef and deep-sea areas
are briefly referred to.
The details which ought to be comprised in a perfect essay upon this subject are so enormous in amount that I have considered it best to offer this paper merely as a "memoire pour servir;" and it is to be hoped that further researches, especially in the deep seas between and beyond the remote islands of the Pacific coral-sea, will clear up some doubtful points.
II. Deep-sea and Abyssal Corals (existing).
Many species of Madreporaria flourish at considerable depths in the seas of Western Europe. The Mediterranean Sea, the Atlantic off the coasts of Spain, France, and Ireland, and the North Sea between the Shetlands and the coast of Norway have yielded to the dredger simple, dendroid, and bush-shaped stony corals at depths of from ten to many hundred fathoms.
These European species have representatives in the deep seas off long lines of continent in many parts of the world. Such forms are sparsely distributed off the western and south-eastern coasts of Africa, the northern sea-board of the United States, and the west coast of the Isthmus of Panama, and they have been met with in the North China Sea and off the coasts of New Zealand and South Australia.
There is a close resemblance in shape and in minute construction amongst these deep-sea corals. Some of the species have great ranges in depth and in area, whilst others are restricted to certain spots. They are never found constituting coral reefs; and but few of the genera to which they belong have contributed forms to the faunas of those aggregations of Madreporaria, or to those of the shallow waters in and about them.
The deep-sea corals are not distributed universally over the sea-bottom. Some places are not coralliferous, and others are crowded with individuals of all sizes of one or more species. All of them are restricted to those portions of the sea-bottom which are remote from the entrance of large rivers, and from flat muddy shores, and which are not in the line of rolling pebbles, where conglomerates can form, or of such sediments as would constantly cover the polypes
