1873.] DUNCAN WEST-INDIA TERTIAEY. 563 



The species of the genera Flabellum, Trochosrailia, Aster osmilia, 

 Circopliyllia, Turbinoseris, and Manicina probably lived in the la- 

 goon, or in deep water outside the reef. 



It is evident that during the period which intervened between the 

 deposition of the Hippuritic Cretaceous strata and those of the Mio- 

 cene, in the West Indies, there were coral reefs flourishing in the 

 N.E. Caribbean, and that the area was one of volcanic activity. 

 The cretaceous deposits of Jamaica, and those of St. Thomas and 

 St. Croix, are probably of the same age, and should be assigned to the 

 same horizon as the Upper Greensand, the " Craie tuffeau," and the 

 Gosau Chalk ; and from the nature of the corals described by Eeuss 

 in Europe, and myself from the West-Indian strata, it may be decided 

 that they were collected together in and about coral reefs. No White 

 Chalk is known in the West-Indian area as yet ; and probably it never 

 accumulated there ; but the Jamaican and the other cretaceous reefs 

 continued to flourish during the deposition of the oceanic sediment to 

 the east, and were not finally overlapped by it, as were the Euro- 

 pean reefs, and also the deposits far away to the north in North 

 America. 



Although there are clear proofs of there having been great altera- 

 tions in the cretaceous reefs and their accumulated deposits in 

 Jamaica before the deposition of any other sediments, still there are 

 no evidences of volcanic activity there. But in the Virgin Islands 

 volcanic ejectamenta are mingled with the cretaceous remains ; and 

 the geology of the district, so ably stated by Mr. Cleve*, proves that 

 a series of volcanic eruptions terminated the Cretaceous period, and 

 that reefs were upheaved and the habitat of the reef-builders was 

 destroyed. 



The volcanic activity was probably a part of the phenomena in- 

 cident to the great crust-movement which witnessed the upheaval of 

 the abyssal deposits of White Chalk. And if this were the case, the 

 equivalency of the coralliferous deposits on either side of the Atlantic 

 was as follows : — 



Eirst. During the age of the Upper Greensand and Chalk Marl, 

 there were reefs in the Caribbean, in Austria, S. France, &c. 



Secondly. The overlap of the White Chalk overwhelmed the Euro- 

 pean reefs during a long period of subsidence ; but the West-Indian 

 reefs were in a volcanic region, and therefore on the edge of areas 

 of unstable equilibrium. They were not on an area of subsidence, 

 and they lasted on. 



Thirdly. The upheaval of the abyssal deposits was accompanied by 

 great volcanic disturbances in the Caribbean ; and the Coral-fauna of 

 the Upper White Chalk of Europe and that of the Jamaican and 

 Virgin-Islands area represented the degenerating coral-life of the 

 period. They differed in species; for the one was younger than 

 the other. 



The Eocene reefs collected around the volcanoes and the upheaved 

 Hippurite-chalk in the Caribbean ; and the examination of their re- 

 mains proves: — 1, that the species may be associated with five Coral- 



* Op. cit. 



