On burrows and tracks of invertebrate animals in Paleozoic rocks, and other markings

The present paper is intended to contribute some recently acquired facts to the solution of questions connected with these often problematical markings; and it will consist rather of short notes, illustrated by photographs, than of a connected discussion of the subject. I propose to notice the nature of certain markings sometimes referred to plants, under the name of Bilobites, —to the true nature of the Scolithus canadensis of the Potsdam Sandstone,—to certain tubes similar to those of modern Sabellæ, —to cylindrical concretions resembling trunks of trees, —and to imitative markings, and peculiar trails of doubtful origin.