LOWER SILURIAN. 



215 



The great St. Lawrence gulf about Ottawa was probably nearly 

 obliterated at this time ; for no rocks later than Lower Silurian occur 

 there until the Quaternary age, just before Man, excepting small 



Fig. 395 Q. — Map of part of Western New England and Eastern New York, showing the belts of 

 limestone. AB, CD, north and south limits of Dutehess County, N. Y. ; B. C , Boston Cor- 

 ners ; Cwl. Br., Cornwall Bridge; Mbb., Mabbitsville ; P. Valley, Pleasant Valley; Sh. She- 

 komeko. Scale l-10th of an inch to a mile. 



patches of Lower Helderberg near Montreal. Thus, the St. Lawrence 

 channel, which was first a short strait between the Archaean areas of 

 Canada and New York, had become much narrowed and lengthened 



