In the Upper Old Red Sandstone,—the formation of the _Holoptychius_ and the _Stagonolepis_,—the only vegetable remains which I have yet seen are of a character so exceedingly obscure and doubtful, that all I could venture to premise regarding them is, that they _seem_ to be the fragments of sorely comminuted fucoids. In the formation of the Middle Old Red,—that of the Cephalaspis and the gigantic lobster of Carmylie,—the vegetable remains are at once more numerous and better defined. I have detected among the gray micaceous sandstones of Forfarshire a fucoid furnished with a thick, squat stem, that branches into numerous divergent leaflets or fronds, of a slim parallelogrammical, grass-like form, and which, as a whole, somewhat resembles the scourge of cords attached to a handle with which a boy whips his top. And Professor Fleming describes a still more remarkable vegetable organism of the same formation, “which, occurring in the form of circular, flat patches, composed each of numerous smaller contiguous circular pieces, is altogether not unlike what might be expected to result from a compressed berry, such as the bramble or rasp.” In the Lower Old Red,—the formation of the _Coccosteus_ and _Cheiracanthus_,—the remains of fucoids are more numerous still. There are gray slaty beds among the rocks of Navity, that owe their fissile character mainly to their layers of carbonized weed; and “among the rocks of Sandy-Bay, near Thurso,” says Mr. Dick, “the dark impressions of large fucoids are so numerous, that they remind one of the interlaced boughs and less bulky pine-trunks that lie deep in our mosses.” A portion of a stem from the last locality, which I owe to Mr. Dick, measures three inches in diameter; but the ill-compacted cellular tissue of the algæ is but indifferently suited for preservation; and so it exists as a mere coaly film, scarcely half a line in thickness.