THE 



CANADIAN NATURALIST. 



SECOND SERIES. 



NOTES ON POST-PLIOCENE DEPOSITS AT RIVIERE- 

 DU-LOUP AND TADOUSSAC. 



By J. W. Dawson, LL.D., F.R.S., F.G.S., Principal of McGill College. 



In looking over, last winter, some of the collections made by 

 Prof. Bell, of Kingston, when engaged in the service of the Geo- 

 logical Survey of Canada, I was struck with a small collection of 

 Post-pliocene shells from Riviere-du-Loup,* as presenting a some- 

 what singular grouping of species ; and having. a few holiday weeks 

 to spend at Cacouna, I determined to ransack thoroughly the de- 

 posits which had afforded these specimens. 



The country around Cacouna and Riviere-du-Loup rests on the 

 shales, sandstones, and conglomerates of the Quebec group of Sir 

 W. E. Logan. As these rocks vary much in hardness, and are 

 also highly inclined and much disturbed, the denudation to which 

 they have been subjected has caused them to present a somewhat 

 uneven surface. They form long ridges running nearly parallel 

 to the coast, or north-east and south-west, with intervening longi- 

 tudinal valleys excavated in the softer beds. One of these ridges 

 forms the long reef off Cacouna, which is bare only at low tide ; 

 another, running close to the shore, supports the village of 

 Cacouna; another forms the point which is terminated by the 

 pier; a fourth rises into Mount Pilote; and a fifth stretches 

 behind the town of Riviere-du-Loup. 



• See Geology of Canada, p. 921, where, however, only a portion 

 of the species collected are mentioned. 

 Vol. II. f No. 2. 



