THE I[RON-FORMATION ON BELCHER ISLANDS 421 
tana,’ and it now seems certain that these low forms of life flour- 
ished well back into pre-Cambrian time, and that they were 
Fic. 6.—The great basalt flows forming Keepalloo Peninsula. The contact 
between two thick flows may be seen near the foot of the hump in the center of the 
photograph. 
Fic. 7.—Ellipsoidal structure which is very common in the basalt flows 
responsible for the precipitation of large bodies of calcareous 
matter whose origin was formerly a matter of doubt. 
tC. D. Walcott, ‘‘Pre-Cambrian Algonkian Algal Flora,” Smithsonian Miscel- 
laneous Collections, Publication No. 2271 (July 22, 1914), pp. 77-150, Pls. 4-23. 
