229 
PHYSICAL AND FAUNAL EVOLUTION 
. 
& 
2 5 
‘ . 
4 2 
wy 
10790 20 
Or 
ys 0 
& | 
oo 
1 
a 
7 
3 
OSS 
Fig. 8.—Paleogeographic map at the end of Trenton time, showing second maxi- 
The currents are indicated for Black River time. 
@® indicates distribution of B. Normanskill graptolites. 
mum transgression in the Ordovicic. 
