On Burrows and Tracks of Invertebrate Animals in Palæozoic Rocks, and other Markings

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Abstract
§Introduction 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. § II. Bilobites, Rusichnites, Protichnites, and Climactichnites. (Fig. 1 to 6.) The name Bilobites , proposed by Dekay in 1823, was as Newberry has shown, originally applied not to objects of this kind, but to casts of certain bivalv shells. It was therefore dropped in America; but it has been revived and has gained currency in Europe†, as a term including various forms of markings referred to different genera. The dominant characters are a band, or an oval mass, with a median longitudinal furrow or ridge, and marked with transverse or oblique furrows or strim, and with or without a marginal ridge. The writer was enabled to show in 1864 that one of the most remarkable of these impressions, Rusophycus grenvillensis of Billings, and Gruziana-like markings associated with it, were really burrows and tracks of marine animals, probably Crustaceans. He arrived at this conclusion by a careful study of the impressions made by the recent

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