458 JOSIAH BRIDGE AND B. E. CHARLES 



St. Francois Mountains, the structural center of the upHft, are 

 directly between the two exposures, and it is not beHeved that 

 these were covered in Devonian time. In view of the thinning 

 out of the Devonian to the north, it may be assumed that the Onon- 

 daga sea extended westward along the southern border of the 

 St. Francois Mountains, and that it may have covered much of the 

 southern portion of the upHft. Further field work may reveal other 

 outHers, which will enable the boundaries of this sea to be traced 

 more definitely. 



