Lacustrine Formation of Torryburn Valley. 5 
reckoned from the time when the latest of the Sax icava or Macoma sands* 
began to be deposited on the Leda clay at the present sea level, then 
the first of the Torryburn fresh-water deposits must be relegated to 
the latter part of the Champlain epoch. It seems, however, more 
correct to regard the Terrace period as overlapping the Champlain, 
and therefore to consider the local deposits of Torryburn Valley 
as beginning in the middle of the Terrace period. 
In the Torryburn Valley there are three depressions which were 
once occupied by ponds of water. Of these hollows, the southern 
one was shallow and was soon silted up; another, the eastern, was 
through the greater part of the Recent period occupied by a shallow 
lakelet, but finally became dry. The third or central depression of 
the valley was much deeper than the others ; it still holds the 
reduced waters of a lake, which once rose to its rocky brim, and is 
known as Lawlor’s Lake. 
The geology and physical history of these basins is of much 
interest in connection with the fresh-water deposits, and will be 
described in a future article, but the following observations are 
confined to a description of the fresh-water deposits only. 
In the process of building the E. & N. A. (now the Intercolonial) 
Railway, a heavy rock-cutting was made at the Western end of 
Lawlor’s Lake, and about 13 feet in depth of its waters were drawn 
off. By this means the beds of shell-marl which underlie the waters 
of the lake were exposed to view, and attracted the attention of certain 
members of this society. Samples of the marl containing fresh- 
water shells were sent to the museum of Comparative Zoology at 
Cambridge, and the peculiar varieties of a species of Valvata occurring 
in them, attracted the attention of Prof. Alpheus Hyatt of Bos- 
ton, who visited the Lake in 1877 for the purpose of examining the 
marl. At his request I undertook to study the geology of the 
deposit, in connection with his proposed work on the biology of the 
mollusca which inhabit its waters and are found in the marl beds. 
To investigate certain doubtful points which had come up, I found 
it necessary to make more careful examinations than I at first 
contemplated, and in the summer of 1880 and 1881, made collec- 
* Macoma groenlandica is a small, lenticular, bivalve mollusc about the size of the human 
thumb-nail, a variety of which, Macoma fusca, is now quite plentiful along the sandy 
beaches of the Bay of Fundy. 
2 
