446 PIISTORY OF GEOLOGY AND PAL/EON TOLOGY. 



and the British Silurian deposits. This preliminary work was 

 followed in the year 1852 by the first volume of his great work 

 on the Silurian system in Bohemia, a work which stands 

 almost unrivalled in palseontological literature. From the year 

 1852 to the year of his death, 1883, Barrande continued the 

 work and produced twenty-two thick quarto volumes with 

 1,160 wonderfully prepared plates depicting the complete 

 fauna of the Silurian basin in Bohemia. He bequeathed 

 means in order that the work should be continued to the end. 



A geological Introduction in the first volume gives a very 

 careful description of the geology of the area. According to 

 Barrande, the stages A and B are "Azoic," and comprise at 

 the base crystalline schists reposing on granite and gneiss, and 

 above the schists, unfossiliferous greywackes, slates, and shales. 

 Stage C contains the oldest (Cambrian) "Primordial fauna," 

 wherein peculiar Trilobite genera predominate. Stage D con- 

 tains the second distinct fauna, the equivalent of the Lower 

 Silurian fauna in the Llandeilo and Caradoc series of Wales, 

 the Champlain group of North America, the Orthoceras Lime- 

 stone of Sweden and Esthland. 



While these horizons, A to D, are chiefly greywackes and 

 shales, the higher stages, E to G, are pre-eminently calcareous. 

 Stage E is distinguished by an exceptionally rich fauna, 

 identical with the Wenlock fauna in the British area. Stages 

 F and G are calcareous, stage H comprises soft shales; in these 

 three stages Cephalopod and fish remains are the most frequent 

 fossils. For this fauna Barrande could not find any equivalent 

 in the palaeontological sequence of the British Silurian deposits, 

 but he assigned the whole complex E to H to Upper Silurian, 

 and regarded it as a third distinct fauna in the palseontological 

 development. 



While Barrande recognised the fundamental agreement 

 between the Silurian horizons determined by him in Bohemia 

 and those already observed in other areas, he remarked on the 

 occurrence of what appeared to be in a measure antecedent 

 "Colonies" of organisms. He found that not infrequently 

 rock-layers containing accumulations of organic types like those 

 of the next higher stage were imbedded in the lower stage; 

 and Barrande explained these "Colonies" by the influx of 

 organisms from certain neighbouring districts in which the 

 fauna had already reached another phase of development. 



Barrande's explanation of the "Colonies" was contested by 



