Histionotus Angularis, was first described and figured by the late Sir Philip de M. Grey Egerton, Bart., F.R.S., in Decade viii. of the Memoirs of the Geological Survey, 1853. The uninterrupted dorsal fin, extending from near the occiput to the tail, suggested the generic name of Histionotus, and in this feature it reresembles Ophiopsis. It has the characters also of other genera, for instance, Pholidophorus in its scales, Semionotus in the shape of its body, and Lepidotus in the shape of its head. Sir Philip Egerton, misled by the imperfect preservation of the posterior end of his specimen, thought the caudal-fin to be also similar to that of Lepidotus.

It has long been recognized by geologists that rock-masses which have undergone movement, and have thereby been subjected to internal stresses, exhibit, as the consequence of the action upon them of such mechanical forces, unmistakeable evidences of having been greatly modified, alike in their mineralogical and in their structural characters. That the most complete and striking examples of such changes are to be found in the rock-masses which constitute mountain-chains—rock-masses which have actually been made to “flow,” and in so doing have been subjected to shearing movements of the most intense character—was clearly pointed out by Scrope, Darwin, Sharpe, Naumann, and Dana; all of whom referred the foliated structure exhibited by such rock-masses to this cause.

The following notes were drawn up by the writer some years since as a sketch for an excursion by members of the Geologists' Association to the Alps, and it may perhaps still prove acceptable to geologists who this year intend to visit Switzerland for the first time.

1. The object of this paper is to show how the soilcap, or its upper portion, may creep down an inclined surface through the action of frost. The subject has also been discussed by Mr. W. C. Kerr in a valuable memoir, “On the action of frost in the arrangement of superficial earthy material,” published in May, 1881. I reproduce here one of the figures given by Mr. Kerr, as I cannot better describe the nature of the phenomenon which it is the aim of this paper to consider.

The Wicklow greenstones occur in sheets and dykes intrusive in the Lower Silurian slates (the equivalent of the Bala beds of Wales) that lie to the east of the main chain of the Leinster granite. Like the Welsh greenstones, they are associated with acid lavas (felsites and keratophyres) and felspathie tuffs, although of slightly later origin than these.

In a paper published in the Devonshire Transactions for 1888 (p. 215), Mr. Somervail suggests the identity of the chlorite schists of South Devon with certain rocks to the northward. As this hypothesis (could it be established) would have a most important bearing on subjects of controversy, I took the opportunity in a few days this winter, to visit and collect from these localities, including the dyke nearest to Toreross. I was not rewarded by finding any striking similarity to the metamorphic rocks of the south. In that series, the chlorite schists consist of clear and definite crystalline grains, among which I find felspar to be rare and have not yet certainly identified augite—while these northern greenstones are full of broken crystals of both minerals, together with viridite, dust resulting from the crushing, and a small amount of minute secondary hornblende and sericite (?), chlorite being generally rare, and often absent.

Thirteen specimens of black shale, crowded with Ostracoda, besides fish-scales, Anthracomyæ (?), and other small fossils, were sent in 1886 by Mr. J. F. Whiteaves, F.G.S., Palæontologist of the Geological Survey of Canada, for examination. They had been collected by Mr. A. H. Foord, F.G.S., of that Survey, in 1881.

Mr. Ami's interesting discovery has already been announced in a letter addressed to Mr. A. H. Foord, F.G.S., published in this Magazine (October, 1888). Mr. Ami now supplies a “Note” on the precise geological position of the beds in which the Turrilepas was found. Want of space, however, precludes us from giving the whole of his detailed observations, which are accompanied by a sketch section, here reproduced:—

The following is a summary of Mr. Ami's “Note.”

The Turrilepas was found in a band of bituminous limestone cropping out on the right bank of the Rideau River, at the Rifle Range, near Ottawa. The precise position of the beds (Lower Utica = about the lower part of the Bala Series), was ascertained by means of their fossil contents, which include an interesting Brachiopod—Siphonotreta Scotica, identified and named by the late Dr. T. Davidson, F.R.S.

A Very important discovery was made independently by Mr. Davison, and somewhat earlier by Mr. T. Mellard Reade, when they demonstrated that, on the hypothesis of the earth having cooled as a solid body, there is within it a certain level, which is called by Mr. Davison the “ surface of zero-strain,” and for which Mr. Reade has adopted the term “ level of no strain.” At this level compression ceases, and for a certain distance beneath it extension, or stretching of the layers of the globe, takes the place of compression.