4 Bulletin of the Natural History Society. 
when this valley was elevated above the sea and occupied by fresh- 
water lakes, can be indicated with considerable exactness. 
The time when the Torryburn deposits began may be arrived at 
from the following considerations : 
The raised beaches and sand flats of the Terrace period in this 
region, which are of Quaternary age and form the connecting link 
with the Torryburn deposits, contain but few mementoes of the Life 
of those times. The “ Saxicava sands” of the St. Lawrence Valley 
which were formed in the Terrace epoch, and were once sand flats 
along the sides of that valley, are characterized by the remains of the sea 
shells, Saxicava rugosa ( arctica ), and Tellina ( Macoma J yroenlandica; 
but in the corresponding deposit near Saint John the former of 
these shells is to a great extent replaced by the Common clam ( Mya 
a,renaria)^ so that it becomes a “ Mya” or “ Macoma” rather than a 
“ Saxicava sand.” Such deposits of the Terrace period can be traced 
down to the present sea level, and there are indications that they 
extend many fathoms below that line. From this we infer that the 
sea at the close of the Terrace period had withdrawn far from the 
present shore line and that the latest Terrace deposits are now con- 
cealed from our view, by tlie return of the sea to its present level 
along the coast. During the time when these changes of land and 
sea were going on, the fresh-water deposit of the Torryburn Valley 
was accumulating. It may be said, therefore, that the Champlain 
epoch had passed away and the Terrace period was considerably 
advanced when the first fresh-water beds were formed in the Torry- 
burn lakes. In this part of Canada the Champlain or Leda clay 
was deposited in ai sea which stood about 200 feet above the present 
sea level ; and in that part of the succeeding Terrace period when 
the divide of the Torryburn Valley was exposed by the rising of the 
land, the sea had shoaled so far as to bring the land up to within 
65 feet of its present level. Two important shore lines marked by 
terraces, had already been raised above the water when the Torry- 
burn lakes first appeared, and two others of equal importance mark 
the slopes along the sea-shore, below the level of the summit of 
Torryburn Valley; the 65 feet level may therefore be considered as 
liolding a middle place in the Terrace epoch, if we suppose that 
epoch to begin when the higher part of the Leda clay was a-wash 
at the sea-level. But if the beginning of the Terrace period be 
