Doubts have been entertained whether the limestone of Burdie House belongs to the Upper Old Red Sandstone or to the inferior Coal Measures. And the fact may yet come to be quoted as a very direct proof of the ignorance which obtained regarding the fossils of the older formation, at a time when the organisms of most of the other formations, both above and below it, had been carefully explored. The Limestone of Burdie House is unequivocally and most characteristically a Coal Measure limestone. It abounds in vegetable remains of terrestrial or lacustrine growth, and these, too, the vegetables common to the Coal Measures--ferns, reeds, and club-mosses. One can scarce detach a fragment from the mass, that has not its leaflet or seed-cone enclosed, and in a state of such perfect preservation, that there can be no possibility of mistaking its character. If in reality a marine deposit, it must have been formed in the immediate neighborhood of a land covered with vegetation. The dove set loose by Noah bore not back with it a less equivocal sign that the waters had abated. Now, in the Upper Old Red Sandstone none of these plants occur. The deposit is exclusively an ocean deposit, and the remains in Scotland, until we arrive at its inferior and middle formations, are exclusively animal remains. Its upper member, "the yellow sandstone," says Dr. Anderson, of Newburgh, "does not exhibit a single particle of carbonaceous matter--no trace or film of a branch having been detected in it, though, if such in reality existed, there are not wanting opportunities of obtaining specimens in some one of the twenty or thirty quarries which have been opened in the county of Fife in this deposit alone." No two bordering formations in the geological scale have their boundaries better defined by the character of their fossils than the Old Red Sandstone and the Coal Measures.