ON THE BRITISH FOSSIL CORALS. 



167 



Great Britain. Rest of Europe. 



Lower Oligocene Scattered reefs Reefs in the Vicentin; deep-sea 



corals in Germany, and 

 littoral species also. 



Crag Deep-sea corals and lit- Deep-sea and littoral species 



toral corals. in Sicily, south of Spain, 



Belgium. Reefs very rare. 



Recent Deep-sea and littoral spe- Deep-sea and littoral species 



cies. in the Mediterranean and 



western seas of Europe. 



The Miocene reefs were in Sonth France, Italy, Spain, and Germany, 

 where thei-e were also deep-sea and littoral species. 



The seas of Europe and Great Eritain during the period of the Middle 

 and Upper Lias were most uucoralliferous, and also during the deposit of 

 the Gault. On the other hand, there were reef and atoll seas during the 

 deposition of the sediments of the zone of A. angulatns and hisiilcatiis of the 

 Lower Lias, of the Inferior and Great Oolite, and of the Oligocene. 



The European area was more or less a centre of oscillation and of reef- 

 formation during the Triassic and the Lower-Liassic periods, duiing the Lower- 

 Oolitic periods, and from the Neocomian to the end of the Miocene, inclu- 

 sive of these periods. There was a great change in the depth of the seas 

 and of the physico-geographical conditions after the formation of the deposits 

 containing A. Biu:Mandi, and a second change produced the reefs of the 

 Oolites. Again, the deposits of the Portland Oolite and the Gault were pre- 

 ceded and followed by gTeat bathymetrical changes. 



The changes on the British area were before the Lower Lias and after it, 

 after the Great Oolite and Coral Rag, and after the Eocene and before the 

 Crag. Whilst the European area was coraUiferous in the Trias, the British 

 area was uucoralliferous ; and whilst the Cretaceous reefs of Western Europe 

 flourished, the British area was characterized by deep-sea and littoral corals. 

 The lines and curves which may be drawn to explain these variations in 

 the two areas are as follows * : — 

 Sea-level. Sea-level. 



* \ / a \ n^ 



y 



A- ^\ 



a. Trias. d. Oolites. g. Cretaceous. h. Miocene. 



b. Lower Lias. e. Neocomian. h. Eocene. I. Pliocene. 



c. Upper Lias. /. Gault. i. Oligocene. m. Recent. 



The reef-areas of the Upper Lias and Gault have yet to be discovered. 



It is very remarkable that the Tabulate corals, which were so abundant 

 in the Palajozoic Coral-fauna, and which constitute whole reefs at the pre- 

 sent time, should not be represented in the British Secondary Coral-fauna. 

 The first trace of them is found in the Eocene beds. The perforate corals, 

 omitting the Eungidte, which are not included in them by MM. Milne-Edwards 

 and Jules Haime, are imknown in the Secondary rocks of Great Britain, 



* The upper diagram refers to the British area, and the lower to the European. Tl.e 

 " a " commences at the upper part of the Trias. 



