62 Rhodora [Marcu 
On the lower Abitibi Thuja occurs, the river for the lower 70 miles 
flowing over Devonian limestones (Wilson, xv.— for 1902~03 — 
233, 235A). On the Kwataboahegan which enters the mouth of the 
Moose River and which “flows over flat-lying, fossiliferous limestone 
for thirty-two miles," “cedar is common" (Wilson, l. e. 229-2314). 
In the great Devonian and Silurian limestone region southwest and 
west of James Bay and Hudson Bay, Thuja does not stop in its north- 
ern extension at the lower Albany River as Hutchinson’s map implies. 
It is found on most if not all of the rivers which enter James Bay from 
the west through this vast limestone lowland. It is on the Kapiskau, 
the banks of which for the lower 125 miles are composed of clay and 
sand " containing marine shells," but higher up of “a very soft reddish- 
brown argillaceous limestone" (Wilson, l. c. 224A); and it extends 
north to the Winisk which enters Hudson Bay in lat. 55? 20' (Wilson, 
l. c.— for 1903 — 103A). 
Hutchinson finds the limits of Pinus Banksiana “irregular” because 
“this species has migrated to 56? N. lat." in Labrador (which is acid 
Laurentian country) but “has been limited in its northward progress 
by the low-lying lands south and westward from James Bay" (the 
calcareous area). Why not reverse the argument and say that the 
limits of Thuja occidentalis are "irregular," since on the low-lying 
country southwest of Hudson Bay it has extended beyond 55? N. 
latitude, while it “has been limited in its northward progress" in 
Labrador by the Laurentian upland? 
On the headwaters of the Severn River, entering Hudson Bay 
northwest of the Winisk, Thuja reaches its northern limit in that 
direction, though it is *a rare tree," nearly the whole country being 
Archaean, “but it occurs on the east end of Slate lake, on Sesikinaga 
lake, on Cedar (Kishikas) lake, and also on Greenshields lake. On 
the shores of the last a few rusty looking trees are growing, and this 
is their northern limit" (Camsell, xvi. 151A). "The whole region is 
granite and gneiss, except for a few limited areas: “The valley of 
Slate lake, which has been formed by the erosion of the soft cale 
schists” (Camsell, l. c. 148A); “Two narrow tongues, however, of 
basic rocks" which “intervene before reaching Gull lake. One of 
these occurs on the Sesikinaga river" (Camsell, l. c. 147A); “basic 
inclusions . . . on the lakeat the head of Cedar river; on the lower end 
of Cedar (Kishikas) lake" (Camsell, l. c. 148A); while “The highest 
hill in the whole area is situated about three miles west of Greenshields 
‘ 
