4 
be considered complete if marks of erosion could be found 
between the two different types of deposit. The possibility of 
erosion having been effected by marine scouring is generally 
given little consideration although it has been repeatedly 
pointed out that such occurs in shallow seas. Barrell, on theor- 
etical grounds, has proved that such must occur and has proposed 
the term, diastem, for the break thus brought about. 1 Kindle 
has lately brought together many of the observations relating 
to marine scouring which have been made by earlier scientists, 
and has presented his own observations relating thereto. 2 
It is a significant fact that the shallow waters about the 
continents contain abundant examples of lateral variation of 
sediments and that few instances of such are recorded in geologic 
literature, whereas the number of unconformities and form- 
ations multiplies in constantly increasing numbers. It is the 
purpose of this article to describe examples of sediment and faun- 
al variation in the shallow Ordovician and Silurian seas in which 
were deposited the sediments which now constitute the rocks 
of the Anticosti sequence, and to show that in these waters 
conditions in respect to the processes and results of sedimenta- 
tion were little different from what they are in seas of the present 
day. 
SECTIONS SHOWING FAUNAL AND SEDIMENT 
VARIATION 
The Anticosti sequence consists of nearly 2,500 feet of 
strata divided into seven formations, three of which are Ordo- 
vician and four Silurian. These formations, named in the order 
of their occurrence from below upward, are as follows: English 
Head, Vaurial, 3 Ellis Bay, Becsie River, Gun River, Jupiter 
River, and Chicotte. 
Darrell, J., Bull. Geol. Soc., Am., vol. 28, 1917, p. 794. 
*Kindle, E. M., Jour.Geol., vol. xxviii, p. 339. 
*The Vaurial formation originally wa s named the Charleton after 
Charleton point, which was believed to be the place of its typical occurrence. 
Thi# was found to be a mistake and it has been renamed the Vaurial, the 
type section being that of Vaurial river. 
