92 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
on the amygdaloid. ‘The trench has, on the other hand, all the appear- 
auce of a subsequent valley worn out in the second cycle by a river 
already well adjusted in an earlier cycle. Finally, we shall see that the 
structure and topography of the Acadian Carboniferous areas will sug- 
gest a subaerial origin for the neighboring Triassic lowland. The broad, 
low, gently rolling plains of the Colchester and Cumberland districts 
flank the Cobequids, and are continuous with the great Carboniferous 
lowland of New Brunswick on the northwest. Their discussion will be 
postponed until the date of the upland facet has been fixed, for this 
date will be found to have an important bearing on the problem of their 
interpretation. 
Granting a subaerial origin for the Triassic lowland, it is natural 
to attempt a scheme for the pre-glacial drainage that conditioned the 
erosion. It is evident that the picture must be incomplete. Much 
of the drainage must have been longitudinal. Some of it was trans- 
verse through courses still well preserved in the notches at Digby 
Gut, Sandy Cove, Petit Passage, and Grand Passage (Plate 7). At 
least two of these are located on faults causing dislocations in the trap 
visible in the field.’ The offsetting of the trap ridge at all four notches 
is most simply explained by as many upthrows on the west. It looks as 
if these faults were older than the upland peneplain, that either a con- 
sequent stream of the former cycle or a later subsequent stream occupied 
each fault-zone, and that the notch in each case was deepened about as 
fast as the adjoining lowlands were worn out. In like manner, the 
Connecticut traversing the Holyoke range in Massachusetts has kept 
open its notch, the product of two cycles. Since the recent drowning of 
southwest Nova Scotia, tidal scour has somewhat widened the passes. 
In passing, it may be noted that the fault at Digby Gut lies close to the 
hinge-line about which I have posited the westward warping of the 
peneplain. 
Tue GroLocicaAL DATES OF THE PENEPLAINS. — In the absence of 
the sediments which must have been deposited on the sea-floor during 
the formation of the peneplain, it is not possible to deduce directly the 
date of the facet in geological time. If I am right in correlating the 
upland facets of North Mountain’and the Southern Plateau, it follows 
that the peneplanation must have occurred in post Triassic times. Beyond 
this general fact, the Acadian record will not permit us to go, except as 
that record is interpreted in terms of better known regions. Using the 
1 Dawson, Acadian Geology, ed. 2, p. 96. Cf. Bailey, Geol, Surv. Canada, Ann. 
Rep. M., 1896, Vol. 9, p. 131, and Dawson, op. cit., p. 95. 
