the stalk of an old-fashioned wine-glass traversed by its thickly-set spiral lines of thread-like china. And so, while on the surface of both the Secondary and Carboniferous coprolites there is space between the screw-like lines for numerous cross markings that correspond to the thickly set veiny branches which traverse the sides of the recent placoid bowel, the entire surface of the Lower Old Red coprolites is traversed by the spiral markings. Is there nothing strange in the fact, that after the lapse of mayhap millions of years,—nay, it is possible, millions of ages,—we should be thus able to detect at once general resemblance and special dissimilarity in even the most perishable parts of the most ancient of the Ganoids? I must advert, in passing, to a peculiarity exemplified in the state of keeping of the bones of this ancient Ganoid, in at least the deposits of Orkney and Caithness. The original animal matter has been converted into a dark-colored bitumen, which in some places, where the remains lie thick, pervades the crevices of the rocks, and has not unfrequently been mistaken for coal. In its more solid state it can hardly be distinguished, when used in sealing a letter,—a purpose which it serves indifferently well,—from black wax of the ordinary quality; when more fluid, it adheres scarce less strongly to the hands than the coal-tar of our gas-works and dock-yards. Underneath a specimen of _Asterolepis_, first pointed out to me in its bed among the Thurso rocks by Mr. Dick, and which, at my request, he afterwards raised and sent me to Edinburgh, packed up in a box, there lay a quantity of thick tar, which stuck as fast to my fingers, on lifting out the pieces of rock, as if I had laid hold of the planking of a newly tarred yawl. What had been once the nerves, muscles, and blood of this ancient Ganoid still lay under its bones, and reminded me of the appearance presented by the remains of a poor suicide, whose solitary grave, dug in a sandy bank in the north of Scotland, had been laid open by the encroachments of a river. The skeleton, with pieces of the dress still wrapped round it, lay at length along the section; and, for a full yard beneath, the white dry sand was consolidated into a dark-colored pitchy mass, by the altered animal matter which had escaped from it, percolating downwards, in the process of decay.