The records of the Geological Survey of Great Britain date back nearly as far as the first public recognition of geology as a science in this country.

The sudden change of strike of the Chalk in South-East Suffolk, exceeded only in abruptness at ,the western limit of the London Basin, is accompanied by Tertiary phenomena equally interesting, and the occurrence of the Palæozoic platform at a small depth under the Chalk in the deep borings at Culford, Stutton, Harwich, and Weeley is, in this connexion, very significant.

It is well known that in various regions of Europe, Asia, and Australia dark pieces of glass are found which, in view of their peculiar shape and sculpturing, have attracted the attention of observers for a good many years. The name of obsidianile was given to these objects by R. H. Walcott. It expresses their resemblance in petrographic nature to obsidian.

There have now been described all the known members of the Edrioasteridae and the very similar genus Stegarioblastus, as well as a genus apparently connected with the Agelacrinidae but presenting some remarkable features, namely Pyrgoeystis. It is proposed in this and the following Study to deal particularly with the Edrioasterid organization, first considering what the known facts of skeletal structure imply as to the general anatomy and mode of life, secondly comparing the structure with that of other echinoderms, especially the Asteroidea. Although it may be necessary to refer to various facts that fall to be dealt with in future Studies, still the present seems a convenient opportunity for this general discussion, because of the recent publication by Mr. W. K. Spencer of the introduction to “A Monograph of the British Palaeozoic Asterozoa” (Feb., 1914, Palæontogr. Soc. vol. for 1913), by Dr. J. F. Gemmill of his highly important memoirs on the starfishes Solaster endeca (1911, Proc. R. Phys. Soc. Edinburgh, vol. 18, pp. 174-91 ; and Feb., 1912, Trans. Zool. Soc. London, vol. 20, pp. 1-71, pis. i-v) and Asterias rubens (Oct., 1914, Phil. Trans., ser. B., vol. 205, pp. 213-94, pis. xviii-xxiv, and March, 1915, Proc. Zool. Soc. London, pp. 1-19, pis. i-iii), and by Dr. A. F. Foerste of some suggestive “ Notes on Agelacrinidæ” (Sept., 1914, Bull. Sci. Lab. Denison Univ., vol. 17, pp. 399-486, pis. i-vi).

In two papers read before the Geological Society in 1904 I showed that the five principal lake basins of sub-Alpine Switzerland lie in a zone which is parallel to the Alps, and that this zone lies almost entirely in the Molasse formation. The conclusions which I drew from these facts as to the age and origin of these basins having, since then, been confirmed by further evidence, it will not be without interest to return to the subject.

Introduction.—The following account of the alteration produced in shale by the sill-like intrusion at Marston Jabet, near Nuneaton, supplements the more general paper dealing with the intrusion as a whole. (See GEOL. MAG., April, 1915, pp. 162-8, Plate VI.)

Last year I received from Colonel Freire d'Andrade a number of interesting alkaline igneous rocks, from a valuable collection made by him during an extensive exploration in North-Western Angola undertaken some years ago. Until recently our knowledge of the geology of that part of Africa was very scanty. Already in 1897 Cornet had described the western tongue of the Belgian Congo which separates the Portuguese provinces of Cabinda and Congo. Moreover, the occurrence of copper ores at Bembe and Senza do Itombe had attracted some geological attention, but it was not until Colonel Andrade's journey that any systematic geological observations were made over a large area of the territory. Since then a number of prospecting expeditions have been conducted by J. J. MacHugh, the results of which serve to extend our knowledge to the south of the area described by Colonel Andrade. In view of the inaccessibility of much of the literature dealing with Angola, it may be interesting, before giving petrological details of some of the rocks, to present in English a short sketch of the geology of part of Portuguese Congo and Loanda, embodying the observations made by Andrade and MacHugh.