[S] Supplement to “Acadian Geology.”
Fig. 8.—Palæophycus Beverlyensis (Billings), a supposed Cambrian Fucoid, but probably an animal trail.
Rhabdichnites and Eophyton belong to impressions explicable by the trails of drifting sea-weeds, the tail-markings of Crustacea, and the ruts ploughed by bivalve mollusks, and occurring in the Silurian, Erian, and Carboniferous rocks.[T] Among these are the singular bilobate forms described as Rusophycus by Hall, and which are probably burrows or resting-places of crustaceans. The tracks of such animals, when walking, are the jointed impressions known as Arthrophycus and Crusiana. I have shown by the mode of occurrence of these, and Nathorst has confirmed this conclusion by elaborate experiments on living animals, that these forms are really trails impressed on soft sediments by animals and mostly by crustaceans.
[T] “Canadian Naturalist,” 1864.
I agree with Dr. Williamson[U] in believing that all or nearly all the forms referred to Crossochorda of Schimper are really animal impressions allied to Nereites, and due either to worms or, as Nathorst has shown to be possible, to small crustaceans. Many impressions of this kind occur in the Silurian beds of the Clinton series in Canada and New York, and are undoubtedly mere markings.
[U] “Tracks from Yoredale Rocks,” “Manchester Literary and Philosophical Society,” 1885.
