In this specimen one valve (the left) and a part of the dorsal region of the other, remain visible; the rest of the right valve being bent down, broken, and imbedded in the matrix. This is a finely micaceous, non-calcareous, grey mudstone, weathering ferruginous towards one edge, which probably abutted on a crack open to water and atmosphere.

The fossil, in the grey portion is darker than the matrix, and fairly represents the test of half of the carapace, with only a very thin lamina wanting, a broken edge of which is traceable (with a lens) near the ventral margin. This left valve measures 9·2 by 7·4 mm. It is subcircular, more boldly curved on the ventral than on the posterior margin, whilst the front margin is somewhat truncate, having a nearly straight edge from above downwards before it bends round into the ventral curve.

In the year 1841 Sir R. Owen described and figured a slab of rock from the Lower Lias of Barrow-on-Soar which showed the impressions of the bones and integuments of a pelvic paddle of an Ichthyosaurus, probably referable to the typical I. communis. In this specimen it appears that the integuments were produced to a greater extent on the posterior than on the anterior side of the bony framework; and that while the anterior margin of the soft parts showed evidence of squamation, the larger posterior flap was marked by oblique striæ extending from the bones to the periphery which appeared to have been caused by parallel bundles of muscular fibres. The distal extremity of the soft fin terminated in a sharp point far below the distal bones.

The stone-rivers of the Falkland Islands have been described by Mr. Darwin, Sir Wyville Thomson, Dr. Coppinger, and other naturalists who have visited those regions. The accounts given by the two first-named are well-known and easily accessible, and render a full description here unnecessary. But it may not be out of place to summarise the principal features of the stone-rivers, which must find an explanation in any satisfactory theory of their origin.

They consist of angular blocks of quartzite, “arranged,” according to Pernéty, “as if they had been accumulated carelessly to fill the ravines.” The blocks are from two to twenty feet long, and rest “irregularly one upon the other, supported in all positions by the angles and edges of those beneath” (Thomson).

Since 1857, the occurrence of a gigantic species of the Selachian family Rhinobatidæ in the Lithographic Stone of Bavaria has been well known, and three fine specimens are exhibited in the Munich Museum. No figure, however, appeared until 1887, when Dr. K. A. von Zittel published the illustration he has kindly allowed to be reproduced here; and the only detailed description is that of Wagner, written about thirty years ago. Quite recently, the British Museum has acquired the counterpart of one of the fossils in the Munich collection—a female individual in a remarkable state of preservation; and this is now exhibited in the form of a slab upon the west wall of the Gallery of Fossil Fishes.

Among instances of the bodily deformation of rocks by lateral pressure, the case of the phyllade aimantifère of Monthermé is well known. By its strong cleavage this rock gives evidence of considerable lateral compression. Professor Renard has shown that prior to this compression the magnetite crystals already existed in the rock, and were surrounded by a coating of chlorite. The crystals yielded to the pressure much less readily than their matrix, and the latter, having already a firm consistence, became separated from the crystals, carrying the chlorite with it, and was displaced along the planes which are now cleavage-planes, that is, in a direction at right angles to that of the pressure.

The genera Phillipsastræa and Smithia have long been a source of trouble to palæontologists, and since the establishment of the latter genus in 1851, it has been very doubtful in which of the two genera certain species of Corals should be placed. The more extended our acquaintance with the species belonging to both genera became, the more probable it seemed that the distinctions between them were in reality unimportant and insufficient to justify a division into two different genera. It was in fact proposed by Kunth as early as 1870 that both genera should be united under the earlier name Phillipsastræa. It has been stated that Phillipsastræa possesses a columella, while Smithia has none; upon the truth of this statement the retention of the two genera depends. Kunth has denied the existence of such a difference. Nevertheless both genera are still retained. From a careful study of the specimens in the British Museum (Natural History) and in the Woodwardian Museum at Cambridge, I have come to the conclusion that Kunth's opinion is well founded; and in the following remarks I shall further attempt to show that certain species which are still sometimes described as having a true columella do not really possess one.

In his memoir on “Modern Denudation,” Dr. A. Geikie determined approximately the number of years required by the following seven rivers to lower the general surface of their basins by one foot. He found that the Danube would take 6846 years, the Mississippi 6000, the Nith 4723, the Upper Ganges 2358, the Rhone 1528, the Hoang Ho 1464, and the Po 729, years. The average of these figures is 3378, and “this,” says Dr. Croll, in his recent interesting work on “Stellar Evolution” (p. 41), “gives a mean of 3378 years to remove one foot, or a little over one-half the time taken by the Mississippi.” As the mean rate of subaërial denudation is an important element in physical geology, it may be worth while to point out a slight mistake in this determination of its value, and also to show how a more correct estimate may, with our present data, be obtained.

During the summer I visited Hof with Professor Nicholson, mainly in order to examine the Graptolite-bearing shales of the surrounding region. These we found to be far from rich in fossils, and the principal fossil-bearing localities were remote from one another. Under such circumstances little could have been accomplished, but for the kindness of Herr Glass, of Hof, who allowed us to examine his fine collection of fossils from the district. To him I would tender my best thanks, as also to Prof. Geinitz, who not only permitted me to examine his rich collection of Graptolites from the Thüringerwald preserved in the Dresden Museum, but also devoted some of his valuable time to me.

For a full account of the Lower Palæozoic rocks of the region under consideration, I may refer to Prof. Gümbel's exhaustive “Geognostiche Beschreibung des Fichtelgebirges mit dem Frankenwalde und dem Westlichen Vorlande.”

At the Meeting of the British Association in 1886, a facetted and striated pebble from the Salt Range, Punjab, was exhibited and described, by A. B. Wynne, F.G.S. Another and larger one was presented by Dr. W. T. Blanford, F.R.S.

During the discussion that ensued, the question was considered whether the stones had received their shapes from the action of windblown sand. Having made a special study of sand-carving in a favourable region, the writer became interested in the subject, and with a view to compare the Punjab stones with the sand-facetted rockfragments so common in various parts of America, wrote to Dr. Blanford in order to obtain specimens of the stones in question. By the kindness of Dr. Blanford and Mr. Wynne, plaster casts of both the specimens described by them have been sent to me.

On De La Beche's Geological Survey Map of Cornwall are three colours representing the associated rocks at, and on each side of the Manacle Point. The Point itself and for a considerable distance south of it is represented as a greenstone. Partially encased in the greenstone and to the south of it is gabbro, which forms the main mass of this rock in the Lizard district. On the north side of the greenstone which forms the extreme south wall of Porthonstock Cove is hornblende-schist, which with some serpentine and other rocks terminates against the killas, or slates near Porthalla.

Several observers with seeming good reason have drawn attention to the fact that the greenstone as represented on the map is made to cover much too large an area to the south, and that any one walking from this direction, or the reverse, finds gabbro where the former rock was expected to occur.