THE UPPER SILUPJAN. 75 



Luwcr Silurian, and to wliicli I shall in the sequel give the name of 

 the Cobequid series, already ai)plied to it in the Table of Forma- 

 tions in Acadian Geology.* 



The euttings of the Intercolonial Railway have enabled Dr lloney- 

 man to recognise at Wentworth, on the north side of the Cobequids, 

 the extension v.'cstward of the Upper Silurian rocks mentioned in 

 Acadian Geology, and also in an earlier memoir on the Metamorphic 

 rocks of Eastern Nova Scotia,f as flanking the crystalline rucks of 

 these hills in New Annan and Earlton. Dr Iloneyman was dis- 

 posed to regard these beds at Wentworth as possibly as old as the 

 Cincinnati group of the Lower Silurian ; but the fossils which I have 

 collected in them seem to me to indicate that they are probably of the 

 age of the Lower Arisaig series,| or about that of the Clinton of New 

 York. They also much resemble in mineral character the Lower 

 Arisaig beds, as well as those of similar age near Cape Gaspe, and on 

 the Matapedia. The more characteristic fossils in my collections arc : — 



Graptolithus Clintonensis, Hall. 

 Climacograpsus and Retiograpsus (?) sp. 

 Atrypa reticularis, Dalman. 

 Strophomena rhomboidalis, Wahl. 

 Lingula oblonga, Hall. 

 Orthis tenuiradiata, Hall, or allied. 

 Orthis elegantula, Dalman, or allied. 

 Rhynchonella neglecta, Hall, ,, 

 Leptocoelia intermedia, Hall, ,, 

 Tentaculites distans, Hall, ,, 



As usual in the shales of this series, the finer markings of the shells 

 are not well preserved, so that it is not easy to assign them to their 

 species. I think, however, that I cannot be wrong in referring them 

 to the lower part of the LIpper Silurian. 



At Wentworth the dark shales holding these fussils are traversed 

 by diabase dykes,§ in the vicinity of which the shales have assumed 

 a gray colour, and have been hardened so as in })laccs to resemble 

 felsites. It is probable tliat the fossiliferous beds may be uncon- 

 formable to the hard slates, felsites, and porphyries underlying them, 

 but the .shales must have participated to some extent in the move- 

 ments to which the older rocks have been exposed. 



* Page 20. f Juurn.al Geological Society, vol. vi. 



I I use the term " I^ower Arisaig" in the sen.se attached to it in Acadian Geology, 

 namely, for the lower fossiliferous series at that jilacc, in the main equi\ali nl to the 

 Clinton and Medina gronjis of New York— Llandovery of England. 



§ See Note W- in Apiicndix. 



