Handbook of Paleontology 293 



pendent arm of the sea extending - from the south north- 

 ward in one of the long troughs of the Appalachian 

 region. 



Two characteristic sections showing the formations 

 of the Canadian and Ordovician systems may be stud- 

 ied : the Lake Champlain section and the section west 

 of the Adirondacks. In the Lake Champlain section, 

 in going from west to east, one passes from the crystal- 

 lines of the Adirondacks across the Potsdam sandstone, 

 Theresa passage beds. Hoyt limestone and Little Falls 

 dolomite of the Ozarkian to the Beekmantown lime- 

 stone (Canadian) which forms the western shore of 

 the lake at many points and has a maximum thickness 

 of 1500 feet. Then come the Black River-Trenton 

 series of limestones of about 300 feet, mostly Trenton 

 (since there is a small representation of Lowville and 

 Leray followed by the Amsterdam with no Watertown 

 present;. Following these beds is a series of black, 

 bituminous shales, the Canajoharie shales (formerly 

 called Utica) which end the section in Vermont, since 

 it is cut oft at the east by a fault. To the west of the 

 Adirondacks the Black river follows for some distance 

 the contact line between the crystallines and sedimen- 

 taries. In the banks here is found the Lowville lime- 

 stone ( Black River series) resting upon the crystal- 

 lines. Lnderneath these beds but not appearing at the 

 surface, because overlapped by the Lowville, are the 

 older formations which appear at the surface farther 

 to the northeast, namely, the Potsdam, a small repre- 

 sentation of the Beekmantown and the Chazy (Pame- 

 lia limestone). The Chazy does not occur in its typi- 

 cal form outside the Champlain valley. Succeeding 

 the Lowville is the Black River (Watertown) lime- 



