Mercer and Warren Counties
In northern Warren and southern Mercer Counties the sandstone underlying the Rock Island (No. 1) Coal is termed the “Stigmarian” sandstone because of numerous siliceous casts found in the bed. Many of the fossils have been collected from an old mine dump and from ravines along the Edwards River northeast of Aledo.
A number of representatives of Sphenophyllum, Neuropteris, and Annularia have been collected from ironstone concretions occurring in shale that overlies the Colchester (No. 2) Coal about three miles southwest of Alexis. They were found in a gully about a third of a mile southeast of Center School.
Plate 3
Pecopteris 1× Ptychocarpus ⅗× Pecopteris ⅗× Mariopteris ⅗× Asterotheca ⅗× Spiropteris ⅗× Pecopteris ⅗×
In the same general area but about three miles due south of Alexis, fossil plants also may be found in the clay pits of the Hydraulic-Press Brick Company and the Northwestern Clay Manufacturing Company.