Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/150

 tive condition of the coral tracts of England and the rest of western Europe. No attention is paid to the existence of land masses.

Great Britain. Western Europe. Reefs. Deep-sea. Littoral. Reefs. Deep-sea. Littoral.

Trias.

Rhaetic.

A. planorbis.

A. angulatus.

A. Bucklandi.

Middle Lias.

Upper Lias.

Inferior Oolite.

Middle "

Coral rag.

Portland Oolite.

Neocomian.

Gault.

Cenomanian.

Lower Chalk.

Upper ".

Eocene.

Oligocene.

Miocene.

Crag-Pliocene.

Recent.

R after an asterisk denotes the paucity of reefs or of deep-sea conditions.

X. Corals and Coralliferous Deposits in consecutive Geological Periods.

The Trias.

There are no vestiges of coralliferous deposits in the British Trias. Formed as a marine deposit, the almost unfossiliferous Triassic sandstones were land- surfaces, whilst there were corresponding tracts reaching far away to the south-east, and great coral-reef areas to the east of the Vosges. The depth of the marine deposits of the Muschelkalk is very great ; and some of them contain compound Madreporaria and some simple forms. The reef origin of much of the dolomite may he inferred ; and the general affinities of the corals of the Muschelkalk and the St.-Cassian deposits indicate successive reefs upon nearly the same area, an elevation of the sediments of the first- named strata having occurred intermediately.

Rhoetic Series.

The subsidence of portions of the Triassic land surface in Britain accompanied the deposition of the Avicula-contorta beds and the White Lias. Some few stunted forms of littoral and deep-sea corals existed in the seas of the period in Great Britain. There were no reefs in our area ; nor are there any evidences of such structures in Europe, except in the Lombardian Alps and to the north of Savoy.

The Azzarolan deposits on the Lake of Como* contain abundance


 * Stoppani, op. cit.