No. 3.3 HUNT — ON CAMBRIAN AND SILURIAN. 297 



lations. He soon found that beneath the horizon characterized 

 by fossils of the Bala group (Llandeilo and Caradoc) there ex- 

 isted in Bohemia a series of strata distinguished by a remarkable 

 fauna, entirely distinct from anything known in Great Britain, 

 but closely allied to that of the alum-slates of Scandinavia, cor- 

 responding to Begiones II. and III. of Angelin. To this he 

 gave the name of the first or primordial fauna, and to the rocks 

 yielding it that of the Primordial Zone. Besting upon the old 

 gneisses of Bohemia appears a series of crystalline schists design- 

 ated by Barrande as Etage A, overlaid by a series of sandstones 

 and conglomerates, Etaye B, upon which repose the fossiliferous 

 argillites of the primordial zone or Etage C. The rocks of the 

 Etages A and B were by Barrande regarded as azoic, but in 

 1861, Fritsch of Prague, after a careful search, discovered in 

 certain thin-bedded sandstones of B, the traces of fiUed-up ver- 

 tical double tubes ; which, according to Salter, [Mem. Geol. Sur. 

 III., 2-13] are probably the marks of annelides, and are identical 

 with those found in the rocks of the Bangor or Longmynd group 

 in Great Britain ; which will be shown to belong to the primordial 

 zone. It is, therefore, probable that the Etage B, which appar- 

 ently corresponds to the Regio Fucoidarum or basal sandstone 

 of Scandinavia, should itself be included in the primordial zone. 

 It may here be noticed that it is in the crystalline schists of A 

 that Gumbel has found Eozoon Bavaricum. To the Etage C in 

 Bohemia, Barrande assigns a thickness of about 1200 feet, and 

 to this his first fauna is confined, while in the succeeding divisinos 

 he distinguished a second and a third. The second f^iuna, which 

 characterizes Etage D, corresponds to that of the B da group; 

 while the third fauna, belonging to the Etages E, F, G and H, 

 is that of the May Hill, Weulock and Ludlow formations of 

 Great Britain. 



■ This classification of the ancient Bohemian faunas was first set 

 forth by Barrande in 1816, in his Notice Freliminaire, in which 

 he declared that the first fauna was below the base of the Llan- 

 deilo of Murchison, unknown in Great Britain, and, moreover, 

 "new and independent in relation to the two Silurian faunas 

 (his second and third) already established in England." This 

 opinion he reiterated in 1859. These three divisions form in 

 Bohemia an apparently continuous series, and being connected 

 with each other by some common species, Barrande was led to 

 look upon the whole as forming a single stratigraphical system ; 



