W. H. Twenhofel — Silurian Section at Arisaig. 143 



Art. XVII. — The Silurian Section at Arisaig, Nova Scotia / 

 by W. H. Twenhofel. With a correlation note by Charles 

 Schuchert. 



[Contributions from, the Paleontological Laboratory of Yale University.] 



While much has been written concerning the Silurian strata 

 at Arisaig and they have often been studied, no section appears 

 in the literature assigning the fossils to their proper horizons. 

 The intermediate position that the fossils of these strata hold 

 in respect to those of the United States and Europe has made 

 such a section particularly desirable. In the summer of 1908 

 the writer, in the interest of the Peabody Museum of Yale 

 University, had the opportunity of making a zonal collection 

 of fossils from this extensive Silurian section and of studying 

 in detail its stratigraphy. 



The writer is under many obligations to Professor Charles 

 Schuchert, without whose assistance in the analysis of the 

 fossils the preparation of this article would have been impos- 

 sible. He is also much indebted to Mr. Alex. J. McDonald 

 and family, in particular, and to the people of Arisaig, in 

 general, for many favors accorded him during his stay with 

 them. 



Review of the Literature. — To the writer's knowledge, the 

 first person to give any definite statement of the geology of 

 northern Nova Scotia was Abraham Gesner, who published in 

 1836 a work entitled : " Remarks on the Geology and Miner- 

 alogy of JSTova Scotia." He divided the rocks of the province 

 into Primary Pocks, Trap Pocks, Clay Slate, and Ped Sand- 

 stone ; the last underlying the northern and northwestern areas 

 (1836 : 1)* 



The first reference to the Arisaig rocks is found in a paper 

 published by J. W. Dawson in 1845, who described the section 

 as follows : "The section between M'Caras brook (top of 

 section) and Arisaig is occupied by dark shales and thin layers 

 of limestone with a few beds of reddish shale and conglom- 

 erate The rocks dip southwest, but become much 



fractured as they approach Arisaig" (1845 : 3). He considered 

 them of Silurian age. 



The first paleontological work on the section appears to have 

 been done about 1850, as in that year Dawson stated that a 

 small collection of fossils from the upper horizon had been sent 

 to James Hall, who expressed the opinion that they belonged 

 to the age of the Hamilton and Chemung groups (1850 : 351), 

 and statements to this effect appear in his Acadian Geology 



* Eeferences are to the list of papers at end of this article. 



