292 



THE GEOLOGIST. 



not represented ; altliongli the genus OrtHs is so ricli in botli coun- 

 tries, it only counts two identical species, and the bulk of the iden- 

 tical forms belongs to the deep-sea group B. M. Barrande has sug- 

 gested that in those cases in which the faunee are distinct in both 

 countries, a limit between both may have existed similar to that now 

 existing between the Red Sea and the Mediterranean, or between the 

 Atlantic and the Pacific, and that when a greater number of identical 

 species' is found, it may be ascribed to the disappearance of this 

 barrier. My view on the subject is different. Supposing that the 

 first and second faunae are indeed httoral and sub-littoral deposits, 

 the presence of open and somewhat deeper sea will alone be quite suffi- 

 cient to account for the distinctness of these faunae, the deep sea 

 forming an almost insurmountable barrier for such beings. Even in 

 the third faunse only such forms will be found identical in both coun- 

 tries, which have been able to pass over the depths of that Silurian 

 ocean which separated Scandinavia from Bohemia. 



Let us for a moment abstract such species as are common to the 

 Bohemia etage/ and to Scandinavia, and only regard the lower etage 

 e of the Bohemian Upper Silurian beds. This deposit offers fourteen 

 species of Brachiopoda, in common with Scandinavia, and, as we 

 have seen above, eleven species in common with the " Colonies." 

 In comparing the lists it is seen, that with the exception of Spiri- 

 gerina reticularis and Stro]?homena euglypha, these two lists contain 

 different names. I presume, therefore, that a further bathymetrical 

 subdivision of that Silurian ocean existed, and that at its southern 

 border the littoral and sublittoral zones were inhabited by the fauna 

 d4t and d5 ; the next deeper by the species found in the " colonies 

 the deepest by those which have proved identical with Scandinavian 

 deposits. Spirig. reticularis and Stropli. euglypha may have lived in 

 both the middle and the deeper zones. 



M. Barrande names about sixty fossils as common to the " colonies" 

 and the fauna e. Among these are eight trilobites and other crus- 

 taceans, twenty Cephalopoda, twelve Acephala, but only eleven 

 Brachiopoda and one Coral : four Cardiolae and eight other Cardiacea 

 are found here, together with four Graptolites. The character of the 

 small list of fossils common to the Upper Silurian of Bohemia and 

 Scandinavia is quite different ; it contains a single Trilobite, very 

 few Cephalopoda, but eighteen Brachiopoda and several Corals. 

 Brachiopoda of the gToup B therefore, and Corals must, if my view 

 be correct, have formed by far the greatest part of the population of 

 the deeper part of the sea. 



Supposed a barrier of land to have existed between Scandinavia 

 and Bohemia, and this to have been destroyed ; no cause can be 

 given Avhy merely Brachiopoda and Corals alone have passed the 

 place where it formerly existed. Say, on the contrary, my view to be 

 correct, then localities must be known in which such Brachiopoda 

 and Corals occur alone, or nearly so, and are contained, not in sand- 

 stone or shale, but in limestone, and these localities may then be re- 

 garded as formed in deep sea. Now such localities are indeed known, 



