34 Reviews— Barrande' s Cephalopoda. 



A fact to be remarked is the occurrence of Goniatites and Gyrocerm 

 in three of the stages, F, G, H, belonging to the Upper Silurian of 

 Bohemia, according to M. Barrande, these genera being at present 

 restricted to the Devonian rocks in the British area, a very interest- 

 ing point, and somewhat suggestive, as — 



Firstly, that Upper Bohemian rocks may represent the Devonian ; 

 or, secondly, that the Silurian forms may have continued longer in 

 the Eastern than the Western area, and were cotemporary with the 

 incoming of new forms ; or, thirdly, that in the portion of the 

 Palaeozoic ocean, now forming Bohemia, certain new generic forms 

 were introduced in the Upper Silurian period, species of which were 

 only developed at a later period in the Western area, or so-called 

 Devonian time. On this point M. Barrande observes in his former 

 work that very few of the characteristic species of his three stages, 

 F, G, H, are found in the Middle or Upper Silurian formations of 

 England, and we must not consider, from their absence, that these 

 parts of the Upper division are not of the same age, but should rather 

 be inclined to believe that the earlier communication between these 

 different regions had been more or less altered. Thus, the deposits 

 may have been isolated in each district, either at the same epoch, or 

 at different times, without our being able to recognize them ; but 

 the times are evidently comprised within the limits of the same 

 period. In a previous paragraph, when ti'eating of his Colonies 

 (or the intercalation of certain species of the stage F amidst a lower 

 fauna, or stage B), the same author remarks : — First, to what extent 

 can the resemblance or palaeontological identity demonstrate that 

 formations geographically isolated from each other, may be contem- 

 poraneous ? Second, to what extent does the dissimilarity between 

 the faunas of isolated and distant basins, correspond to a difference 

 in the epoch when the deposits were accumulated? These are 

 questions intimately related to the laws of the diffusion and distribu- 

 tion of species, little stu,died at present, but the bearings of which 

 are ably treated by Prof. Huxley in the Anniversary Address to the 

 Geological Society, for 1862. 



In comparing the Silurian rocks of Bohemia with those of 

 Sweden, M. Barrande points out that notwithstanding the great 

 difference in thickness between the two countries (30,000 feet in 

 Bohemia to 12,000 in Sweden) they each possess three general 

 faunas. Li both cotmtries the Primordial fauna is composed almost 

 exclusively of Trilobites, distinguished generally by the great de- 

 velopment of the thorax and the small pygidium. 



The second fauna of both countries has the maximum development 

 of Trilobites belonging to new types, in which the pygidium is 

 large and the thorax reduced, of which about three-fourths existed 

 in both countries, whilst the third fauna presented a greater har- 

 mony in this group, more than three-fourths having co-existed in 

 each country, a contrast to Brachiopods which presented few comr 

 mon species, and the corals were very different. 



The conclusion being, that the parallel between Bohemia and 

 Scandiuavia shows, that the general renewal of life in these ancient 



