Abstract
Summary: Limestones and cherts from the Crow Series near Richmond are described and their origins discussed. Many of the limestones contain some dolomite, and almost all are more or less siliceous; there is no clear distinction between the siliceous limestones and the cherts, most of which contain some calcite. The rocks are thought to have originated by the penecontemporaneous alteration of shell-fragments and other organic calcareous debris. The great majority of the abundant sponge-spicules, now composed of calcite, dolomite, or silica, are thought to have been originally calcareous.