the Devonian Rocks of Moravia. 70 



corals, including the Ccntenipora escharoides, so characteristic 

 of the Silurian rocks, and which has never yet been found in the 

 Devonian, together with the Terebratulu linguata and T. imbri- 

 crtto or wm;:!7i/;afe of Dalman, which occur in the upper Silurian 

 rocks of Wenlock and Dudley in England, and of Gothland in 

 Sweden.* In speaking of the contemporaneity of the trap- 

 rocks of this part of the Silurian series of Bohemia, to you who 

 have so distinguished yourself in this department of our 

 science, I must explain myself. Some of the greenstones and 

 amygdaloids in question have certainly been erupted in 

 amorphous masses, which have broken irregularly through 

 the limestone and shale, and have often, to a great extent, 

 fractured, indm-ated, and altered them. Such masses have, 

 therefore, fairly burst through pre-existing, strata ; but this 

 erupHon having terminated, the bottom of the sea in whicli 

 the phenomenon occurred, evidently resumed, to a great ex- 

 tent, its tranquillity ; for the upper portion of the plutonic 

 rock assumes a bedded form, and is followed in the ascend- 

 ing order by numerous thin courses of " schaalstein," inter- 

 laminated with black schists and nodular limestone, all of 

 which strata are conformable over considerable areas. Tiiis 

 phenomenon, which I have studied in other countries, even 

 Siberia, in company with De Verneuil and Keyserling, I 

 have always thought can only be explained either by sup- 

 posing that the cinders or ashes derived from the eruptive/o« 

 were regenerated into deposits with alternating courses of 

 calcareous mud, or, as is more probable, that successive par- 

 tial disturbances of the sea-bottom furnished fresh subma- 

 rine volcanic materials during a certain period, until the 

 volcanic action entirely ceased.f The lowest member of the 

 upper Silurian Rocks of Bohemia is overlaid by limestones of 

 considerable thicknesses, which M. Barande has very pro- 

 perly divided into two formations (/ and g of section), by ob- 

 serving, that however united in physical aspect, each is dis- 



• See Miirchison's Description of the Silurian Rocks of Sweden, Journal of the 

 Geological Society of London. 



t Here, us in the Rhenish provinces, Britain, and elsewhere, organic re- 

 mains occasionullv occur in the " Schaals^tcin." 



