on which turbot, halibut, and large skate are found. Numerous boats were stretching down the Moray Frith, bound for the banks of a more distant locality, frequented at this early stage of the herring fishing by shoals of herrings, with their attendant dog-fish and cod; and I knew that in yet another deep-sea range there lie haddock and whiting banks. Almost every variety of existing fish in the two friths has its own peculiar habitat; and were they to be destroyed by some sudden catastrophe, and preserved by some geologic process, on the banks and shoals which they frequent, there would occur exactly the same phenomena of grouping in the fossiliferous contemporaneous deposits which they would thus constitute, as we find exhibited by the deposits of the Lower Old Red Sandstone. The remains of Holoptychius occur, I have said, in the neighborhood of Thurso. I must now add, that very singular remains they are,--full of interest to the naturalist, and, in great part at least, new to Geology. My readers, votaries of the stony science, must be acquainted with the masterly paper of Mr. Sedgwick and Sir R. Murchison "On the Old Red Sandstone of Caithness and the North of Scotland generally," which forms part of the second volume (second series) of the "Transactions of the Geological Society," and with the description which it furnishes, among many others, of the rocks in the neighborhood of Thurso. Calcareo-bituminous flags, grits, and shales, of which the paving flagstones of Caithness may be regarded as the general type, occur on the shores, in reefs, crags, and precipices; here stretching along the coast in the form of flat, uneven bulwarks: there rising over it in steep walls; yonder leaning to the surf, stratum against stratum, like flights of stairs thrown down from their slant position to the level; in some places severed by faults; in others cast about in every possible direction, as if broken and contorted by a thousand antagonist movements; but in their general bearing rising towards the east, until the whole calcareo-bituminous schists of which this important member of the system is composed disappear under the red sandstones of Dunnet Head. Such, in effect, is the general description of Mr. Sedgwick and Sir R. Murchison, of the rocks in the neighborhood of Thurso. It indicates further, that in at least three localities in the range there occur in the grits and shales, scales and impressions of fish. And such was the ascertained geology of the deposit when taken up last year by an ingenious tradesman of Thurso, Mr. Robert Dick, whose patient explorations, concentrated mainly on the fossil remains of this deposit, bid fair to add to our knowledge of the ichthyology of the Old Red Sandstone. Let us accompany Mr. Dick in one of his exploratory rambles. The various organisms which he disinterred I shall describe from specimens before me, which I owe to his kindness,--the localities in