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138 to which they add a by no means inconsiderable bulk, certainly support, to some extent, M. Virlet d'Aoust's hypothesis of the origin of organically formed oolite by means of ova, if not always due to insects' eggs; and the entanglement of similar eggs in the clay of ponds also shows how insects may have exercised an agency, however slight, in the formation of some other stratified deposits. If to these evidences of insectal agencies, we add the probable fact, that the surfaces of many shales of various geological ages bear the trails of insects, as intimated above, pages 129 and 131, we have stronger proofs than we had heretofore of the wide-spread and long-continued existence of Insects in past ages of the world.

To get better and clearer notions, we want more carefully observed and recorded facts than we have hitherto had at command. Let us get good observations on the crawling and burrowing creatures of the sea-shore and pool-sides, of sand- and mud-banks, and alluvial flats; let us get good dried specimens or good drawings for comparison; and let us carefully collect and collate fossil surface-markings, noting what are real surfaces and what are casts on the lower sides of the laminæ and strata, and we shall then be doing good work towards the elucidation of Ichnolites of all descriptions.

Before concluding, I must offer an observation on the Climactichnites Wilsonii, Logan,—a gigantic trail-like tract found in the Potsdam Sandstone of Canada, and described and figured by Sir W. E. Logan, in the 'Canadian Naturalist and Geologist,' 1860, vol. v. p. 279, etc. In this paper, Sir William lucidly describes the probably littoral condition of the Potsdam Sandstone, extending for many miles along the old Laurentine Hills, and its evidences of tidal phenomena. The Climactichnites is associated at Perth, in Canada, with the Protichnites, tracks found also in other parts of the Potsdam Sandstone of Canada, and described by Logan and Owen in 1852, in the Geological Society's Journal, vol. xiii. p. 199, etc., plates 6–14a. Of the Canadian Protichnites, there are six different kinds or species, according to Prof. Owen; they are all of large size, from about three to ten inches broad, and are referred to Crustaceans, possibly of the Limuloid type, that have crawled over the surface of the sand. Protichnites of smaller size have been found in the Silurian rocks of Scotland, at Binks, Roxburghshire, by Prof. R. Harkness ('Quart. Journ. Geol. Soc.,' vol. xii. p. 243, fig. 2); and another, from the Coal-measures of South Wales, has been figured and described by Mr. Salter, in the 'Memoirs of the Geol. Survey, etc.: Iron-ores of South Wales,' 1861, p. 227, pl. 2, fig. 24.

The Climactichnites is described as a trail about 6$3⁄4$ inches broad; and it is not dissimilar, in its transverse bars, to fig. 1c of Mr. A. Hancock's plate (XIV., see above, p. 131), illustrative of the natural gallery-track of the little sea-shore crustacean, Sulcator arenarius. I would suggest that the Climactichnital tracks were really infallen gallery-tracks, formed, like those of the Sulcator, by burrowing Crus-