No. 4.] HUNT — ON CAMBRIAN AND SILURIAN. 445 



upon crystalline schists. The Primal division was regarded by 

 the Messrs, Rogers as the equivalent both of the Potsdam and 

 the still lower members of the Cambrian. 



Auroral, (11.) This division, which, with the last, includes 

 the first fauna, consists in great part of magnesian limestones, 

 and corresponds to the Calciferous and Chazy formations. Its 

 thickness in Pennsylvania varies from 2500 to 5000 feet, and 

 with the preceeding division, it includes the first fauna. The 

 representatives of the Primal and Auroral divisions attain a great 

 development in eastern Tennessee, where they have been studied 

 by Safi"ord. 



Matinal, (III.) In this, which represents the second fauna, 

 were comprised the limestones of the Trenton group, together 

 with the Utica and Hudson-River shales. 



Levant, (lY .) This division corresponds to the Oneida and 

 Medina conglomerates and sandstones. 



Siirgent, Scalent and Pre- Meridional (V. VI.) In these 

 divisions were included the representatives of the Clinton,. 

 Niagara and Lower Helderberg groups of New York, making, 

 with division IV., the third fauna. 



The parallelism of these divisions with the British rocks was 

 most clearly and correctly pointed out by H. D. Rogers himself, 

 in an explanation prepared, as I am informed, with the collabora- 

 tion of Prof. William B. Rogers, and published in 1856, with a 

 geological map of North America by the former, in the second 

 edition of Keith Johnson's Physical Atlas. The paleozoic rocks 

 of North America are there divided into several groups, of which 

 the first, including the Primal, Auroral and Matinal, is declared 

 to be the near representative of " the European paleozoic deposits 

 from the first-formed fossiliferous beds to the close of the Bala 

 group ; that is to say the proximate representatives of the Cam- 

 brian of Sedgwick.'.' A second group embraces the Levant, 

 Surgent, Scalent and Pre-Meridional. These are said to be 

 *' the very near representatives of the true European Silurian, 

 regarding this series as commencing with the May-Hill sand- 

 stone." The Levant division is farther declared to be the equi- 

 valent of the sandstone just named ; while the Matinal is made to 

 correspond to the Llandeilo, Bala or Upper Cambrian ; the Auroral 

 with the Festiniog or Middle Cambrian ; and the Primal with 

 the Lingula flags, the Obolus sandstone of Russia and the Pri- 

 mordial of Bohemia. 



