The contents of a Geological Journal form as miscellaneous a series as can well be imagined. In its pages all kinds of subjects meet the eye together: the analysis of an obscure mineral on one page; the correction of a stratigraphical error on another: here is a fresh reading of an old text; and there an uninviting catalogue with synonyms. Occasionally the Journal looks like the note-book of a naturalist; and the affinities of a genus, the migrations of species, and the ‘theory of descent with modification,’ are discussed with zealous care: and then, again, we get back to the old times and old subjects of geological thought; and Werner and Berzelius, and their followers, have it for a season all their own way. There is nothing to complain of in all this: it is just what it ought to be; for it shows how wide our subject-matter is. ‘The earth andall that is therein’ — that is surely wide enough; nor will pen, pencil, or graver, till the end of time, have done with it. It is not one of the least of the charms of our comprehensive science, that every one may add something to its stores. A sea-side walk, with a hammer in the pocket, may discover a new world by accident; for, as Darwin, Lyell, and Ramsay have told us, the unrepresented past tunes have been far greater than those of which we have a geological record, and fragments of the missing pages may turn up at any time.

The object of the present communication is to review and compare the characters of the Tertiary and Recent species of Thecidium, the true characters of which have been discovered only within the last few years. The genus was first named Thecidea by Defrance in 1821, and corrected into Thecidium by George Sowerby 1823.

On the northern margin of the Firth of Forth, opposite Edinburgh, a line of steep craggy slope sweeps round from behind the village of Burntisland to the shore about half a mile eastward. The highest and most precipitous portion rises to a height of 631 feet; and the space between its base and the shore is so short that when seen from a short distance, the hill seems to shoot almost directly out of the sea. Hence these heights form conspicuous landmarks all over the Lothians. Their scarred fronts and verdurous slopes bear all the characteristic features of the minor hills in the lowlands of Scotland — a union of brown mouldering crag, often steep and bold, with soft green hollows, and with shelving sides that are either cumbered with ruins from the cliff overhead, or dotted with bushes of golden gorse. Such scenery is to a geological eye eminently ‘trappean;’ it at once suggests beds of greenstone, basalt, and ash, with the other concomitants of ancient volcanic eruptions. And truly amid all the rich development of volcanic phenomena in these Lowlands, the rocks of the Burntisland shore deserve to stand up as conspicuous landmarks. They have been laid bare by rains and frosts and the waves of the Firth along some miles of the coast-line, where they can be studied, bed after bed, in the minutest detail. I know of no such section in any other part of the kingdom.