254 
AUG. F. FOERSTE 
On Bear Island the younger dolomite series of the Heclahook 
system is underlaid by the slate-quartz series ^ and the latter 
by the older dolomite series.. These older dolomite rocks contain 
oolitoids and stromatolites, both chemical precipitates of car- 
bonate of lime induced by the chemical activities of primitive 
plants; some of the stromatolites are of the Cryptozoon type, 
others are of the Gymnosolen type. The lower dolomitic rocks 
are correlated with the Ozarkian of North America. 
From these studies by Dr. Holtedahl it is evident that three 
American series of Ordovician rocks had a wide distribution in 
Arctic areas; these are the Ozarkian, Canadian, and Black River. 
All three are recognized on Bear Island, and all three appear to 
have their lithological equivalents on Spitzbergen. Moreover, the 
two lower series appear to be represented also in Finmarken at 
the extreme northern end of Norway. Here the Ozarkian or 
older dolomite series of Bear Island is represented by the Por- 
sanger series, and the Canadian or younger dolomite series of 
Bear Island finds its equivalent in the Varanger and Raipas 
series. 
The Canadian age of the strata exposed at Durness, in the 
extreme northwestern corner of Scotland, has been known for a 
long time owing to the occurrence there of the very diagnostic 
species Piloceras invaginatum Salter. Orthoceras'mendax Salter 
is an annulated form with a relatively large subcentral siphuncle 
which may turn out to be a Protocydoceras^ a typical Canadian 
genus. Three species with very oblique annulations occur; 
these are Orthoceras haculoides Blake, Orthoceras durinum Blake 
and a form identified as Orthoceras arcuoliratum- (?) Hall. In 
Orthoceras durinum the siphuncle probably is marginal. The 
general aspect of these species is Canadian. If their siphuncles 
were better known they probably would prove related to the 
Endoceratidae rather than to the Orthoceratidae. Orthoceras 
pertinens Blake, however, appears to be a typical Orthoceras, 
Among other forms identified from the Durness limestone are 
Ophileta compacta Salter and Maclurites matutinus (?) Hall, 
both of which are typical Canadian forms. 
