456 Prof. T. Sterry Hunt — On Cambrian and Silurian. 



darum 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 Bavaricnm. 

 To Etage G in Bohemia, Barrande assigns a thickness of about 

 1200 feet, and to this his first fauna is confined, while in the suc- 

 ceeding divisions he distinguished a second and a third. The second 

 fauna, which characterizes Etage D, corresponds to that of the Bala 

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

 -H, is that of the May Hill, Wenlock and Ludlow formations of 

 Great Britain. 



This classification of the ancient Bohemian faunas was first set 

 forth by Barrande in 1846, in his Notice Preliminaire, in which he 

 declared that the first fauna was below the base of the Llandeilo of 

 Murchison, unknown in G-reat 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 con- 

 tinuous 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 ; and finally to assert that these three 

 independent faunas " form by their union an indivisible triad which 

 is the Silurian system," (Bui, Soc, Geol. de Fr., ser. ii. vol. xvi. 

 pp. 529-545.) Already, in 1852, in his magnificent work on the Silurian 

 System of Bohemia, Barrande had given to the strata characterized 

 by his first fauna the name of Primordial Silurian. It is difficult to 

 assign any just reason for thus annexing to the Silurian — already 

 augmented by the whole Upper Cambrian or Bala group of Sedg- 

 wick (Llandeilo and Caradoc) — a great series of fossiliferous rocks 

 lying below the base of the Llandeilo, and unsuspected by the author 

 of the Silurian System ; who persistently claimed the Llandeilo beds, 

 with their characteristic second fauna, as marking the dawn of 

 organic life. 



Up to this time the primordial Palaaozoic fauna of Bohemia and of 

 Scandinavia was, as we have said, unknown in Great Britain. The 

 few organic remains mentioned by Sedgwick in 1835 as occurring 

 in the region occupied by his Lower and Middle Cambrian, on 

 Snowdon, were found to belong to Bala beds, which there rest upon 

 the older rocks : nor was it until 1845 that Mr. Davis found in the 

 Middle Cambrian remains of Lingula. In 1816 Sedgwick, in com- 

 pany with Mr. Davis, re-examined these rocks, and in December of 

 the same year described the Lingula-beds as overlaid by the Trema- 

 doc slates and occupying a well-defined horizon in Caernarvon and 

 Merionethshire, beneath the great mass of the Upper Cambrian 

 rocks. (Geol. Journ. vol. ii. p. 75; vol. iii. p. 139.) Sedgwick, at 

 the same time, noticed about this horizon certain Graptolites and an 

 Asaphus, which were supposed to belong to the Tremadoc slates, but 

 have since been declared by Salter to pertain to the Arenig or Lower 

 Llandeilo beds, the base of the Upper Cambrian. (Mem. Geol, Surv,, 

 vol. iii. p. 257, and Decade ii.) 



This discovery of the Lingula-flags, as they were then named, and 



