BAERAIS^DE COLONIES. 3 



the classes, except tiie Cephalopods, being largely represented in g 1, 

 while the Cephalopods are more numerous in g '3, in the proportion 

 of 3 to 2 (p. 54). 



g 2 and h 1 may be similarly distinguished. The two beds toge- 

 ther contain 54 species. Of these, about 16 species occur in the 

 lower beds which do not occur in the higher, while the higher con- 

 tain two species only which are not found in the lower. The two 

 highest members of H are unfossiliferous and are not therefore liable 

 to be confounded with the shale below. 



Comparing the Silurian system of Bohemia with that of England, 

 M. Barrande finds that while a complete correspondence exists be- 

 tween the grand divisions, it does not extend to the minor ones. 

 Thus the fossils which characterize the Upper Silurian system of Eng- 

 land and the " third fauna " of Bohemia, considered as a whole, con- 

 stitute one and the same general fauna, which, at its commencement, 

 presented very close relationship, but which, from local or other causes, 

 underwent in each country a different evolution, and hence that the 

 different zones in the two countries as distinguished by their fossils 

 are merely local subdivisions which have no correspondence, although 

 comprised in the same period of time during which the Silurian sy- 

 stem was being deposited. Thus we find that of the 2000 species 

 which characterize the third fauna of Bohemia and the 500 in England 

 there are only 57 species in common, 32 of which had existed previ- 

 ously in British Lower Silurian rocks, although some of them do not 

 appear in the second fauna in Bohemia. Of these 57 species, 50 

 occur in the Wenlock, and 27 in the Ludlow rocks, and one passes 

 up into the passage-beds. In Bohemia 51 of these 57 species are 

 found in stage E, 12 in stage E (7 being recurrent species), 5 in stage 

 G (4 being recurrent species), and 1 in stage H {Lingula cornea) 

 (pp. 175 & 176). 



It appears, therefore, that, abstracting the passage-beds, the Upper 

 Silurian fauna of England is sufficiently (maniere satisfaisante) re- 

 presented in the stage E of Bohemia, and that stages E, 0, and H of 

 the Prague Basin, and especially the two last, are not certainly present 

 in England (p. 177). 



To render this more clear it may be well to state that the chief 

 palseontological characters of G are (1) the predominance of Trilobites, 

 and especially of Dalmanites and Bronteus, and the presence of Caly- 

 mene in the horizon of ^ 1 ; (2) the reappearance of Cephalopods of 

 the genera Phragmoceras and Gomphoceras in g 3, which had disap- 

 peared at the close of stage E ; (3) the appearance of Gonatites, rela- 

 tively considerable, analogous to those of the Devonian system which 

 had already been ushered in by some rare forms in stage F ; (4) the 

 sporadic appearance of Coccosteus smd Asterolepis*, hitherto generally 

 considered as exclusively proper to the Devonian period. These 

 elements are entirely wanting in England, not only in the Wenlock 

 and Ludlow rocks, but even in the passage-beds. If, therefore, we 

 give to palseontological evidence the value we have hitherto attributed 

 to it in the classification of deposits, and above all in the comparison 

 * Carboniferous? 



b2^ 



