514 



GEOLOGY 



382. Map showing the general condition of the North Amorir.-m conti- 

 nent in Mid-Ordovician (Trenton) time. The black portions n-pn--. nt 

 areas where the Middle Ordovician beds appear at the surf:ici>. These 

 areas so nearly correspond with the areas where the Ordovician system 

 as a whole appears at the surface, that no serious error is involved it' 

 the black areas be interpreted as Ordovician. The various conventions 

 of the map are the same MS in Fi<r. 358, p. 477. 



