I12 FRANK D. ADAMS 
while on the Atlantic shores, far north, is found a great group present- 
ing many like features. West of James Bay and south of Hudson 
Bay, rocks lithologically like the Nastapoka series underlie a hilly 
district rising like an island above the surrounding flat-lying Paleozoic 
beds. In this great district of the pre-Cambrian west of Hudson 
Bay, large areas bordering the Arctic about the mouth of the Copper- 
mine River, and extending to Great Bear Lake, are underlain by a 
development of rocks resembling in nearly all respects the Nastapoka 
series and similar rocks have been described from the region about 
Great Slave Lake. 
In all these widely separated localities great developments of 
the same rocks occur and often are accompanied by beds of jaspilite 
and iron ore. Everywhere the members present the same general 
arrangement, the strata cut by many faults, dipping at comparatively 
low angles and forming ridges frequently capped by diabase, while 
in most cases the beds have been found overlving with a most striking 
unconformity older granitic and gneissic rocks. These points of 
similarity seem to indicate that the scattered groups are all of about 
the same age and belong to a pre-Cambrian series probably at one 
time nearly continuous over the northern regions from the shores 
of the north Atlantic to about the valley of the Mackenzie. In Labra- 
dor and in the districts west of Hudson Bay the evidence indicates 
that the Nastapoka series was deposited after an epoch of severe 
erosion. Lake Mistassini, in northern Quebec, lies in a basin-like 
depression occupied by nearly flat-lying beds of cherty dolomite 
representing a portion of the Nastapoka series, while south of the 
lake these rocks have been found almost in contact with a develop- 
ment of the Lower (or Middle) Huronian, differing in no essential 
features from this group of rocks as found in numerous localities 
further southwest toward Lake Superior. ‘The Lower Huronian is 
in a highly disturbed condition and has been penetrated by large 
bodies of granite. Neither the disturbances nor the granitic intrusions 
have affected the near-lying Nastapoka series so that the latter seems 
to be undoubtedly of post-Lower (or Middle) Huronian age, to have 
been formed after the Lower Huronian had been folded and invaded 
by the granites and then deeply eroded. The relation of the two 
series resembles that existing between the Animikie and Lower Huro- 
