Description. Body elongated, narrow, composed of a longitudinal series of eight imbricating plates, and marginal girdle (?) of spicules.

It is a noteworthy feature of the most ancient crystalline limestones that they are generally dolomitic, or at any rate frequently so. They often consist of practically pure dolomite; whilst associated with this in some cases is pure crystalline magnesite, which is very liable to be mistaken for saccharoidal dolomite.

The mining village of Foxdale, situate a little towards the southern end of the north-east to south-west central trend-line of the Isle of Man, lies just north of the barren heath-covered hill called “Stoney Mountain”. On the 6 inch Ordnance Survey Map the northern part of this hill is called Granite Mountain and the southern portion Windy Common. The whole forms a long, regularly sloped hill with its greatest length—about 2 miles—approximately north and south. Though of small altitude its singular barrenness makes it conspicuous in a moderately well-cultivated district. To the west South Barrule and the Barrule Slate Quarries rise considerably above it, though on the other sides the ground slopes gently off to more distant hills.

The chemical evidence with relation to the formation of a laterite from a diabase was given in a paper in the March number of the GeologicalMagazine, pp. 120–3. Since that account was written I have made microscopical examinations of the materials therein described.

The latest book on metamorphism, Dr. V. Grubenmann's Kristallinen Schiefer, still leaves it an open question what a metamorphic rock is. Generally speaking there is no doubt about the matter; every geologist has a more or less precise idea of what he means by the term, but no one has yet been able to propound a definition which is perfectly satisfactory, and which will enable one to distinguish a metamorphic rock from all other kinds and at the same time convey an expression of the characteristic peculiarities inherent in such a rock. The need of a definition is very necessary. The want of it has led Dr. Grubenmann to include some rocks among the crystalline schists which one ordinarily would not refer to that class, and on the other hand there are some rocks frequently referred to that class which are not included. In the first case, the masses of emery form the twelfth group of Dr. Grubenmann's classification, yet the analysis of the Naxos emery, which reveals traces of boric oxide (1.15 per cent. in one case) would seem to place these lenses among the ore-bodies deposited by pneumatolitic action.

As long ago as 1836 Prestwich published his historical paper “On the Geology of Coalbrook Dale”, and in it he figured a Crustacean carapace under the name of Apus dubuis.