No. 2.] THE "colonies" of m. barrande. 189 



matter, except occasional concretions of carbonate of lime. The 

 Superior Division is composed almost entirely of calcareous mat- 

 ter, with merely subordinate bands of schists and quartzites. 

 Each division can be satisfactorily broken up into four sub-divi- 

 sions (etages), grounded solely upon the characters of their con- 

 tained fossils, and lettered in ascending order : — 



The dtages of the Inferior Division are A., B., C, D. The 

 dtages of the Superior Division are E., F., G., H. Each of the 

 fossiliferous sub-divisions can be further broken up into minor 

 groups or " bands," distinguished by the smaller letters of the 

 alphabet, as shown in the annexed table. 



Etages A. & B., the lowest of the Inferior Division^ are com- 

 posed of semi-crystalline rocks and conglomerates, and are unfos- 

 siliferous. They are termed by Barrande the "Azoic Etages," 

 and are considered by him as forming the base of the Silurian 

 Series. It is, however, more probable that they should be re- 

 garded as being truly of Lower Cambrian age, 



Etages C. D. E. F. G. & H. are fossiliferous. Etage C. is the 

 well-known " Primordial Zone " of Bohemia, corresponding with 

 the Menevian beds of Britain, and characterized by primordial 

 trilobites of the genera Faradoxides, Olenus, Conocori/phe, Ellip- 

 tocephalus, &c. It should probably be regarded as Upper Cam- 

 brian. 



Etage D. contains Barrande's so-called " faune second " or 

 second fauna, and must correspond with the Llandeilo and Cara- 

 doc beds of Britain. Etages E. F. G. & H. are characterized by 

 a single fauna termed by Barrande the " faune troisieme " or third 

 fauna ; and they correspond collectively to the Upper Silurian 

 Rocks of Britain. 



The precursors (" avanteureurs ") of this "third fauna" in 

 the last portions of the period of the " second fauna " are termed 

 by Barrande the " colonies." They are in the form of bands 

 which are enclosed in the mass of (^tage D towards its higher part, 

 and which are thus stratigraphicallij Lower Silurian, but which, 

 nevertheless, contain a predominance of fossils characteristic of 

 the "third fauna," and thus comQ palceontologically to belong to 

 the Upper Silurian series. They abound especially in the band 

 d 5, occurring also in d 4, and about twenty of them are known 

 in all. The subjoined table shows in a summary form the 

 general subdivisions and lithology of the rocks of the Bohemian 

 basin, with the principal characteristic fossils: — 



