Key to Divisions ---------------- C - Cambrian Rocks. S - Silurian System. D - Devonian. Ch - Champlain Division. On - Ontario Division. He - Helderberg Division. Er - Erie Division. Divisions as recognized Divisions as recognized Pennsylvania Ohio. by English Authors. by the New York and Virginia. Geologists. /-------------------\ /-----------------------\ /----------\ /--------\ { Upper Cambrian { { Potsdam Sandstone. } No. 1. { { { C { Rocks, of Sedgwick{ { Calciferous Sandrock. } { { { Birdseye Limestone. } No. 2. } { (probably). {Ch{ Trenton Limestone. } } Blue { { } Limestone { Llandeilo Flags. { { Utica Slate. } } and Marl. { { { } No. 3. } { { Hudson River Group. } { { { { { Gray Sandstone. } No. 4. { { { Oneida Conglomerate. } { {On{ { Caradoc Sandstone.{ { Medina Sandstone. } No. 5. { { { Clinton Group. } { { Niagara Group. { { } } { { { Oneida Salt Group. } : { { { Water-lime Group. } : { { { Pentamerus Limestone. } No. 6. : { { { Delthyris Shaly } : { { { Limestone. } : S { { { Encrinal Limestone. } : Cliff { Wenlock Rocks. {He{ Upper Pentamerus } : { { { Limestone. : Limestone. { { { Oriskany Sandstone. } : { { { } No. 7. : { { { Cauda-Galli Grit. } : { { { Schoharie Grit. } : { { { Onondaga Limestone. Wanting. : { { { Corniferous Limestone. Wanting. } { } { { { Marcellus Shales. } } Black { { { Hamilton Group. } } Slate. { Upper and Lower { { } No. 8. { { { Tully Limestone. } { Ludlow Rocks and {Er{ } : { { Genesee Slate. D : the Devonian { { } : { { Portage Group. } No. 9. } Waver : System. { { } } { { {Chemung Group.