CONTENTS. 
XIII 
General features. 151 
Localities. 156 
Thickness. 157 
Mineral contents. 157 
Organic remains. 157 
22. CORNIFEROUS LIMESTONE. 161 
General features. 161 
Subdivisions .. 161 
Localities. 167 
Thickness. 168 
Mineral contents... 168 
Springs. 168 
Agricultural characters .. 170 
Organic remains. 170 
23. Marcellus shale. 177 
General features and extent. 177 
Localities. 179 
Thickness... 179 
Minerals. 179 
Springs. 179 
Agricultural characters. 179 
Organic remains. 180 
Localities of superposition. 183 
24. Hamilton group. 184 
1 . Dark slaty fossiliferous shale. 187 
2. Compact calcareous blue shale ... 187 
3. An olive, or often bluish fissile shale, 187 
4. Shales of Ludlowville. 187 I 
5. Encrinal limestone. 187 
6 . Moscow shale. 187 
Joints or vertical cleavage. 192 
Concretions. 192 
Localities. 193 
Thickness. 194 
Mineral contents. 194 
Springs. 194 
Agricultural characters. 194 
Organic remains. 195 
Localities of superposition. 211 
25. Tully LIMESTONE.212 
Extent and general characters.212 
Concretionary structure.214 
Localities •••• .214 
Thickness. 214 
Mineral contents.214 
Organic remains. 215 
Remarks preliminary to the following 
rocks and groups.217 
26. Genesee slate.210 
General characters, extent, etc.218 
Concretions. 220 
Localities. 220 
Thickness. 221 
Minerals. 221 
Organic remains.221 
27. Portage or Nunda group.224 
General character and extent.224 
Subdivisions. 226 
1. Cashaqua shale. 226 
2. Gardeau shale and flagstones.227 
3. Portage sandstones.228 
Diagonal lamination. 230 
Ripple marks. 230 
Casts of shrinkage cracks.230 
Concretions. 230 
Casts of flowing mud. 332 
Casts of mud furrows and striae.234 
Localities. 237 
Thickness.238 
Minerals. 239 
Springs. 239* 
Agricultural characters. 239 
Organic remains. 241 
Localities of superposition.248 
Ithaca group . 250 
28. Chemung group. 251 
General characters and subdivisions.. 251 
Diagonal lamination and structure of 
strata. 256 
Concretions. 257 
Spheroidal desquamation...257 
Ripple marks.•. 257 
Localities. 258 
Thickness. 260 
Mineral contents. 260 
Springs. 260 
Agricultural characters. 260 
Organic remains. 261 
Localities of superposition.276 
