1 L'»i McLeam — Silurian Arisaig Series of Arisaig, N. S. 



Art. X. — The Silurian Arisaig Series of Arisaig, Nova 

 Scotia;* by F. H. McLearn. 



Introduction. 



The Silurian section of Arisaig has more than one 

 claim to importance and is responsible for the reputation 

 of this place in geological literature. As the most con- 

 tinuous and longest ranging of its age in eastern Canada 

 it serves well as a type exposure, by comparison with 

 which the more fragmentary occurrences of less favoured 

 localities may be integrated and assigned to their true 

 position in the stratigraphic column. It is interesting 

 because of the resemblance of its faunas to those of 

 Great Britain and for the light it sheds on the paleogeo- 

 graphic relations of the North Atlantic to the interior 

 seas of America. The unusual faunal associations, and 

 in particular the rich development of bivalves, also 

 attract attention. 



Previous studies. — The section possesses considerable 

 historic interest and has been studied by the geologists 

 and paleontologists of three generations. Among them 

 may be mentioned Abraham Gesner, J. William Dawson, 

 James Hall, Eev. David Honeyman, E. Billings, Hugh 

 Fletcher, Henry M. Ami, Charles Schuchert, W. H. 

 Twenhofel, and M. Y. Williams. Briefly the work 

 already done at Arisaig may be stated as follows : The 

 general geological problems, igneous, structural and 

 physiographic, and the correlation of the Ordovician 

 have been treated at length by M. Y. Williams (1914) 1 . 

 In Silurian stratigraphy, the section has been finally 

 divided into five formations whose delimitations and 

 thicknesses have been determined by Twenhofel (1909). 

 These have been correlated with interior North America 

 and Kristiania, Norway, by Schuchert and Twenhofel 

 (1909) and with Anticosti by Twenhofel (1913). The 

 important and necessary direct comparison with the 

 British succession has been almost entirely neglected. 

 There has also been no correlation with the neighboring 

 section of Eastport, Maine. The identifications and zonal 



* Published with the permission of the Director of the Geological Survey, 

 Canada. 



1 Since a complete bibliography will be given in the final monograph, only 

 the year of publication of the works cited is thought necessary here. 



