Mc Learn — Silurian Arisaig Series of Arisaig, N. S. 135 



with the Upper Llandovery to form a single correlative 

 unit. This unit, then, compares not only with the Arisaig 

 Ross Brook, but also with the American Clinton (not 

 including the Irondequoit). 



The McAdam and Moydart are together correlated 

 with the Salopian without regard at present to its com- 

 ponent divisions. The Stonehouse compares very well 

 with the marine zones of the Downtonian, i. e., with the 

 Aymestry, Upper Ludlow and also the lower part of the 

 Downton sandstone. This is based on the following: 

 Lingula minima Sowerby, Dalmanella lunata (Sowerby), 

 Br achy prion gilpini (Dawson) cf. B. ornatella (Salter), 

 Grammy sia triangulata (Salter), G. obliqua (McCoy) 

 and Orthonota angulifera (McCoy). 



Eastport, Maine. — Comparison with Eastport, Maine, 

 indicates that the Edmunds fauna is intermediate in devel- 

 opment between the Arisaig Moydart and Stonehouse 

 faunas. Its duration may in large part be equivalent to 

 the time represented at Arisaig by the "red bed" sub- 

 aerial stage. The Eastport Pembroke formation corre- 

 lates with the Stonehouse while the earlier Quoddy and 

 Dennys compare with parts at least of the McAdam and 

 Moydart. 



Interior America, etc. — Comparisons with interior 

 North America, Anticosti, and Kristiania, Norway, prac- 

 tically follow those of Schuchert and Twenhofel (1909). 

 The same difficulty is met with in correlating with the 

 later Silurian of interior North America, but this is 

 shown to be the result of the paleogeographic relations 

 that prevailed in post-McAdam-Rochester time. 



The Knoydart problem. — The age of the Knoydart and 

 its relation to the Arisaig series will be discussed in 

 detail in the final report. It may be said that the faunal 

 evidence is non-committal and the structural evidence 

 obscure. The topographic conditions of the late Silu- 

 rian, however, were more favourable for the building out 

 of deltas into the sea than were those of the Lower 

 Devonian. The evidence of the geologic setting, there- 

 fore, favors a Silurian age. 



Paleogeographic relations. 



While the affinities of this fauna are chiefly trans- 

 Atlantic and with Great Britain, it also shows relation- 



