Mr. A. G. Nathorst, whose recent contributions to the Palæobotany of Sweden have been very valuable, has been turning his attention to the impressions found on the surface of schists, especially in Palæozoic rocks, which have been too readily accepted as impressions of plants. They find a place among the Algæ of Schimper's “Traité de Paléontologie Végétale,” and they are employed by Saporta and Marion in their recent work, “L'Evolution du Régne Végétal,” and are treated as Algæ, and employed as data in their account of the evolution of the vegetable kingdom. Mr. Nathorst, so long ago as 1873, called in question the plant origin of many of these markings, and he has recently published in the Transactions of the Royal Swedish Academy (vol. xviii. No. 7, Stockholm, 1881) an exhaustive treatise on the subject, with eleven phototypic plates of impressions which he obtained by the motions of different animals or the trails of plants on soft materials.