ROCKS OF BOHEMIA. 



617 



species have not hitherto been recorded from Bohemia ; some of them 

 have been found by myself at the base of the main Silurian beds ; 

 and others would I feel sure be found if searched for. The list is 

 as follows : — 



Monograptus spinigerus, Nich. 



triangulatus, Harkn. 



Becki, Barr. 



cyphus, Lapw. 



tenuis, Portl. 



■ proteus, Barr. 



Rastrites peregrinus, Barr. 

 capillaris, Carr. 



Diplograptus Hughesii, Nich. 



folium, His. 



com eta, Gein. 



■ tamariscus, Nich. 



• sinuatus, Nich. 



Climacograptus scalaris, His. 

 Discinocaris Browniana, Woodw. 



All these fossils, including the Discinocaris of which Herr Dusl 

 possesses three specimens, are characteristic of the Birkhill Shales of 

 Britain. 



§ 6. Summary. 



In very many of the Predevonian rocks of Bohemia we find 

 marked lithological resemblances to the corresponding horizons in 

 Britain. 



The Precambrian series is divisible into two distinct groups, 

 similar to the Dimetian and Pebidian groups of Britain, and lying 

 unconformably to one another and to the overlying Cambrian rocks. 



The beginning of the Cambrian period is marked, as in Britain, by 

 a coarse conglomerate, which is probably of later formation than that 

 of our own island, although it is probably homotaxeous with it. 

 Moreover, there are strong resemblances between the various bands 

 of the Bohemian and British Cambrian beds, especially marked in 

 the deeper water deposits. The palseontological similarities are in 

 many cases not so striking as the lithological. 



In the Silurian period, the resemblances, both lithological and 

 palgeontological, between Bohemia and Britain were less striking 

 than in the Cambrian. The limestones so abundant in the Bohemian 

 series seem to be lenticular masses having no wide extension ; the 

 most regular limestone is that of E 2, and this is about the horizon 

 of, and comparable with, the Wenlock Limestone. But although the 

 beds of this period as a whole are not so strictly comparable in the 

 two countries as those of the Cambrian, we nevertheless find most 

 remarkable coincidences between the zones of the lowest band, i. e. 

 the Graptolite- bearing shales. 



The igneous rocks do not present many unusual features ; but the 

 occurrence of mica-traps in the Cambrian beds is very noteworthy, 

 limited as they are, so far as yet known, to Predevonian rocks. 



Objection may be raised to my using Prof. Sedgwick's nomencla- 

 ture for the rocks of a region which M. Barrande has so conclusively 

 shown to possess three well-marked faunas. But the foregoing 

 observations seem to show that the break between the upper and 

 middle faunas is much more marked than that between the middle 

 and lower. In the first place, the deposition of the Cambrian beds 

 does not seem to have beo;un over the whole area until the close of 



