are the oldest Liasic rocks anywhere seen in Scotland. They are composed chiefly of greenish-colored fissile sandstones and calciferous grits, in which we meet a few fossils, very imperfectly preserved. But the organisms increase as we go on. We see in passing, near a picturesque little cottage,--the only one on the shores of the bay,--a crag of a singularly rough appearance, that projects mole-like from the sward upon the beach, and then descending abruptly to the level of the other strata, runs out in a long ragged line into the sea. The stratum, from two to three feet in thickness, of which it is formed, seems wholly built up of irregularly-formed rubbly concretions, just as some of the garden-walls in the neighborhood of Edinburgh are built of the rough scoria of our glass-houses; and we find, on examination, that every seeming concretion in the bed is a perfectly formed coral of the genus Astrea. We have arrived at an entire bed of corals, all of one species. Their surfaces, wherever they have been washed by the sea, are of great beauty: nothing can be more irregular than the outline of each mass, and yet scarce anything more regular than the sculpturings on every part of it. We find them fretted over with polygons, like those of a honeycomb, only somewhat less mathematically exact, and the centre of every polygon contains its many-rayed star. It is difficult to distinguish between species in some of the divisions of corals: one Astrea, recent or extinct, is sometimes found so exceedingly like another of some very different formation or period, that the more modern might almost be deemed a lineal descendant of the more ancient species. With an eye to the fact, I brought with me some characteristic specimens of this Astrea[4] of the Lower Lias, which I have ranged side by side with the Astreae of the Oolite I had found so abundant a twelvemonth before in the neighborhood of Helmsdale. In some of the hand specimens, that present merely a piece of polygonal surface, bounded by fractured sides, the difference is not easily distinguishable: the polygonal depressions are generally smaller in the Oolitic species, and shallower in the Liasic one; but not unfrequently these differences disappear, and it is only when compared in the entire unbroken coral that their specific peculiarities acquire the necessary prominence. The Oolitic Astrea is of much greater size than the Liasic one: it occurs not unfrequently in masses of from two to three feet in diameter; and as its polygons are tubes that converge to the footstalk on which it originally formed, it presents in the average outline a fungous-like appearance; whereas in the smaller Liasic coral, which rarely exceeds a foot in diameter, there is no such general convergency of the tubes; and the form in one piece, save that there is a certain degree of flatness common to all, bears no resemblance to the form in another. Some of the recent Astreae are of