182 PALEOZOIC TIME. 



struction of the Acadian life above mentioned, and the additional 

 observation, by F. H. Bradley, that at Henry's Lake, Idaho, a quartz- 

 yte (probably Potsdam) underlies unconformable the beds of the 

 Quebec group. The fact, stated by Emmons, that pebbles of the Pots- 

 dam sandstone are included in a conglomerate at the base of the Cal- 

 ciferous, seems to show that the consolidation of the Potsdam had 

 taken place before the Calciferous era. 



2. CANADIAN PEEIOD. 

 1. American. 



Epochs. — 1. The Calciferous, or that of the Calciferous sand- 

 stone of New York, etc. 2. The Quebec, or that of the Quebec 

 group in Canada. 3. The Chazy, or that of the Chazy limestone. 



The rocks of the extensive Quebec group were first distinguished 

 and described in Canada by Canadian geologists, and all the subdivi- 

 sions are well represented there ; and hence the period is named the 

 Canadian. 



I. Rocks : their kinds and distribution. 



The rocks of the earlier section of this period — the Calciferous — 

 are a calcareous sandstone and magnesian limestone in Canada and 

 northern New York, adjoining the region of the Potsdam sandstone ; 

 and the same, more purely limestone, with some shales, along the Ap- 

 palachians ; but, in the Mississippi basin, mainly magnesian limestones, 

 with some small intervening sandstone beds, excepting to the north, 

 where sandstone prevails. Those of the second section — the Que- 

 bec — consist of shales, with some sandstone and thin limestone strata 

 near Quebec ; limestone chiefly in the Appalachian region of East 

 Tennessee, and also in the Rocky Mountain region, in Utah, Idaho, 

 and also Wyoming Territories. Those of the third — the Chazy, so 

 named from a locality in Northern New York — are limestone in New 

 York and Western Canada, outcropping near the Calciferous out- 

 crops : and magnesian limestone in part of the Mississippi basin ; the 

 same, but of greater thickness, to the southwestward along the Ap- 

 palachian region in Pennsylvania and Virginia — though the beds are 

 not wholly distinguished from the limestone of the Trenton period. 



Through the discovery of fossils near Rutland, in Vermont, it has 

 been shown by Billings, that part of the great crystalline limestone of 

 the Green Mountain region is of the Chazy epoch. 



The St. Peter's sandstone, overlying the Lower Magnesian lime- 

 stone of Wisconsin and Iowa, is referred to the Chazy epoch ; and the 

 sandstone along the southern and part of the northern shores of Lake 

 Superior, including the " Pictured rocks," is regarded by Hall as rep- 



