By the kindness of Mr. B. N. Peach, F.R.S.E., F.G.S., of the Geological Survey of Scotland, I have been permitted to examine a very interesting insect-remain enclosed in a light-brown nodule of Clay-Ironstone, obtained fram Kilmaurs, Ayrshire.

In February last I had the pleasure to describe three new forms of British Carboniferous Cockroaches, viz.:—

1. Etoblattina Johnsoni, H. Woodw., Coal-Measures, Coseley, near Dudley.

2. Leptoblattina exilis, H. Woodw. do. do.

3. Lithomylacris Kirkbyi, H. Woodw., U. Coal-Measures, Meithil, Fife.

Mr. S. H. Scudder, of Boston, has described no fewer than 30 species from the Coal-Measures of N. America, whilst 41 species have been described by Goldenberg, Heer, Germar, Scudder, and others from the Coal-Measures of Europe, so that this group of Orthopterous insects was perhaps almost as well represented in the Coal-period as at the present day, and nearly as widely distributed geographically.

The first references in any detail to the nature of the Chert in Carboniferous rocks appeared in 1878, when Messrs. Hull and Hardman published a joint paper on the subject, treating more particularly of the Chert in the Upper Carboniferous Limestone of Ireland. Prof. Hull gave a general description of the distribution and mode of occurrence of the Chert, and a detailed notice of its microscopic structure, as shown in fifteen thin sections of the rock from various localities in Ireland. Prof. Hull gave a general description of the distribution and mode of occurrence of the Chert, and a detailed notice of its microscopic structure, as shown in fifteen thin sections of the rock from various localities in Ireland. The author reached the conclusion that the Chert is essentially a pseudomorphic rock, consisting of gelatinous silica replacing limestone of organic origin, chiefly foraminiferal, crinoidal, and coralline; the replacement was believed to have taken place before the shales overlying it were deposited, whilst the limestone was in a more or less plastic condition, admitting the fine percolation of water holding silica in solution. The sea was believed to have been largely charged with silica in solution, and the chemical process was accelerated by the warm surface waters of a shallow sea. The origin of the Chert from the siliceous skeletons of Biatomaceas, Polycystinas, and the spicules of sponges is distinctly denied, and it is affirmed that it can only be considered as a secondary product due to the replacement of lime-carbonate by silica.

The shells of Cephalopods form an evolutionary series, traceable to an ancestor unknown, but nearly related to not yet coiled forms of the Cambrian. In all descendants from this common stock homologous parts are discerned. Hence facts regarding the growth of any one form may be applied to all. Of Cephalopods with chambered shells only Nautilus, Spirula, and Sepia exist. Spirula is so rare and its shell so retrograde that no theory has yet been built on it. Examination of Nautilus gave rise to the Secretion-hypothesis, shortly stated as follows:—As the animal grows, the adherent muscles and the cincture gradually advance, the siphuncle lengthening in proportion; thus a cavity is formed between the last septum and the surface of the visceral hump: this latter then deposits calcareous matter, beginning at the sides of the shell and proceeding towards the siphuncle round which it is continued backward. During the advance of the animal the anterior portion of the mantle secretes calcareous matter, which it deposits in successive layers on the margin of the aperture (Edwards and Wood).

The specimen under notice is relatively shorter, broader (higher), more triangular, and with sharper ridges than the figure in the ‘Monograph,’ 1856, pl. vii. f. 21. The anterior hinge is more prominent, and the front margin rather oblique. It is also narrower behind, ending with three small spines or denticles. The edge viewis acute-ovate. From the Belosepia-bed, Bracklesham. T. R. Jones’ Collection.

It had not been my intention to publish anything on this subject at present, as I have in preparation a review of the present state of our knowledge of Himalayan geology; but as Col. McMahon has started the subject, and his paper is not exhaustive, I trust the following outline of that part which relates to the gneissose rocks may prove of interest.