ANNIVERSARY ADDRESS OF THE PRESIDENT. XXXV 



Bohemia, if not created in place, arrived by currents having their 

 origin in the S.W. If, however, as now suggested, contortions of the 

 strata have deceived this able observer, an argument of this kind can 

 have no weight. 



Of the four stages of Upper Silurians in Bohemia, the three lower 

 divisions are typically calcareous, and the culminant section schistose. 

 The lowermost has a base consisting of traps alternating with black 

 slates containing Graptolites, and including occasional concretionary 

 limestones. It attains a thickness of not more than 900 feet, but has 

 a fauna superlatively rich and prolific in fossil treasures. Between 

 500 and 600 species of organic remains have been collected in this 

 formation. In it is found the maximum number of species of Tri- 

 lobites, no fewer than 78 ; and several genera, including Harpes, 

 Bfonteus, and Froetus, appear for the first time in Bohemia. Cepha- 

 lopoda abound ; as many as 200 species, of which half are Orthocerata, 

 have rewarded the collector. Ascoceras, Gomphoceras, and Phrag- 

 moceras are the characteristic types. Gasteropods, Lamellibranchs, 

 and Brachiopods are numerous, and there are not a few Zoophytes. 



The second or middle stage of Upper Silurian limestones presents 

 a decreasing fauna, but at the same time exhibits the maximum of 

 Brachiopoda. Bryozoa and Tentaculites appear, and Cephalopoda 

 rapidly diminish in numbers. 



Between the third or upper stage of these limestones and the last 

 there is a gradual passage, and in these fishes commence and Brachio- 

 pods have become rare. A considerable number of species in this 

 division are enumerated as common to it and the two last. 



In the uppermost stage of culminating schists the community of 

 species is reduced to two Trilobites, and the entire fauna is poverty- 

 stricken. Traces of vegetables indicate some considerable changes 

 in the conditions of the sea-bed. 



The four upper stages, constituting in their aggregate the Upper 

 Silurians of Bohemia, contain a fauna (the third fauna of Barrande), 

 which, as a whole, is regarded by its describer as of equal importance 

 with the first or primordial fauna, and the second or chief Lower 

 Silurian fauna. The strongest relations of identity of species between 

 the Bohemian Silurians and those of other regions, are exhibited by 

 the third or Upper Silurian fauna. A curious point concerns the 

 second, viz. that it is represented in France not only by the same 

 genera but also by identical species, whilst in England and Sweden it 

 is represented by the same generic types and a great analogy of 

 distinct specific forms. Of the different classes of animals it would 

 appear that but few Crustacea are common to other countries, whilst 

 the Cephalopoda, Brachiopoda, and Corals are widely diffused. The 

 evidences of communication between the Silurian series of different 

 regions are clearly indicated, and everywhere the distinction between 

 his three great faunas is maintained by M. Barrande to be plainly 

 exhibited. At the same time he pronounces definitely for the unity 

 of the Silurian group as a well-characterized whole. 



I would now call attention to the results of his inquiries into the 



c 2 



