72 On (he Silurian Bocks of Bohemia, and 



applied, whether in Europe or America ;* and in proceeding 

 from that protozoic division to the next in ascending order, he 

 cannot fail to remark, that many masses of eruptive rocks are 

 interpolated, some of which have been most certainly formed 

 contemporaneously with the ordinary sedimentary strata. The 

 lowest of these eruptive rocks contains already more lime, 

 whether inamygdaloidsor disseminated, than is to be detected 

 in all the subjacent lower Silurian strata ; and each superior 

 course of this eruptive matter is more and more charged with 

 carbonate of lime in a basis of felspathic greenstone. In truth, 

 when the rock alternates with the graptolite schist and lower 

 limestone of Barande, {e of section), it is perfectly undistin- 

 guishable from many of those bands of " schaalstein" which 

 are familiar to you, as well as other German geologists iu 

 Nassau, and is not unlike some of the contemporaneous Silu- 

 rian volcanic grits described by me in Shropshire and Rad- 

 norshire, or the " volcanic ash" of De la Beche. In Nassau 

 the " schaalsteins" are subordinate to true Devonian rocks, 

 but in Bohemia they occur in the lowest stage of the upper 

 Silurian division (e). This stage is instructively displayed 

 on the left bank of the river Beraun, below the town of that 

 name, where it is clearly seen to repose on the schists and 

 quartzose rocks, or upper beds of the lower division, and is 

 surmounted by the limestones (/, (/, and k). The bottom 

 beds contain numerous forms of the most beautiful grapto- 

 lites I ever saw. Thin layers of black limestone occur, and 

 then the shales contain round and spheroidal nodules of 

 black earthy limestone, in which M. Barande has found 

 many of his best fossils. Bands of " schaalstein," passing on 

 the one hand into a coarse-grained greenstone, and on the 

 other into amygdaloidal trap, succeed, imtil the group gra- 

 duates upwards into a solid limestone, usually of dark colour, 

 which is absolutely loaded with Orthocoratites, Phragmoceras, 

 and other chambered shells, and is also peculiarly distin- 

 guished by containing Carcliolw. The surfaces of the upper 

 portion of these lower limestones are marked by numerous 



* De Vcrneuil's Table of Classification of the Paleozoic Fossils which mutu- 

 allj' occur in Xorth America anrl Europe. Bulletin dc la Soc. Geol. de France, 

 1847. 



