It may interest our readers if we remind them that with the publication of our July Number the Geological Magazine enters upon the fiftieth year of its existence. The first number was issued in July, 1864, and the first volume consisted of six numbers for the half-year. Consequently the commencement of the fiftieth Volume took place in January of the present year. It must be a matter for congratulation to the Editor that during so extended a period he has personally edited every number, excepting three, when he took a long vacation in Italy and could not conveniently deal with proofs. Such a record is probably unique. It is moreover satisfactory to learn that there has at no time been a serious lack of useful material wherewith to fill the pages of the Magazine. In our copy of Vol. I there are lists of Local and Foreign Correspondents; among the former is the name of the Rev. H. H. Winwood, and among the latter are the names of Baron Adolph. von Koenen and Dr. Anton Fritsch. Amongst surviving contributors to the 1864 volume may be recorded the Rev. Osmond Fisher, Sir Archibald Geikie, Professor Edward Hull, Sir E. Ray Lankester, and Henry Woodward.

Some years since Professor E. J. Garwood sent to me for examination some pieces of limestone from the Lower Carboniferous rocks in the Shap and Ravenstonedale districts of Westmorland, in which he had observed the rounded outlines of fossils with a structure which appeared to him to resemble that of Stromatopora. The rock in which the fossils were embedded was so compact and hard that they could not be extracted, and it was necessary to make sections in various directions in order to ascertain their structure, which proved to be identical with that of Solenopora, now well known as one of the calcareous Algæ. It is many years ago since this genus was recognized in the Ordovician rocks in North America, Britain, and Eussia; more recently it was found in the Silurian rocks of the Isle of Gotland, and in 1894 a species was described from the Jurassic rocks of Gloucestershire and Yorkshire. But until this fortunate discovery of its occurrence in the Lower Carboniferous by Professor Garwood, no example of the genus was known in any of the rocks between the Silurian and the Jurassic.

More than fifty years since a great impulse was given to the study of a new and strange group of Palæozoic Arthropoda whose remains were almost simultaneously brought to light in New York, in England, Scotland, and in the Baltic island of Oesel, and attracted the attention of numerous palæontologists both in this country and in America. Among others may be cited Hugh Miller and the elder Agassiz, who at first believed them to be fish (1844), but the latter afterwards was convinced that they were in reality the remains of an enormous Crustacean.

Some years ago Mr. D. M. S. Watson and I collected, from the Carboniferous Limestone of Clitheroe, Lancashire, a considerable series of Echinoids. One slab of the limestone (measuring 16 × 12 cm.) is covered by a great number of disjointed plates and other skeletal fragments of a large Perischodomus, probably P. bliserialis, M'Coy. Dr. R. T. Jackson refers to the specimen (Phylogeny of the Echini, p. 406), and, as the jaw fragments show features not hitherto described for the genus, it seems advisable to give a brief account of it. The preservation of a compass is a point of special interest, as these delicate structures are known in very few cases in the fossil state.

The species described in this paper is based on specimens acquired for the Geological Department of the British Museum in 1912 from Professor C. Klouček, of Prague, who collected them from the upper portion of D γ (=Arenigian) at Šárka and Malé Prilepy. The fossil was referred in the first instance by Professor Klouček to “Chiton sp. ?” and the result of the present investigation has been to uphold the reference to the Polyplacophora, though the precise generic status must remain vague.

The Riebeckite-Orthophyre of the Holy Isle.—Four Occuxrences of acid and sub-acid igneous rocks containing the rare soda-amphibole riebeckite have been recognized in Great Britain, of which that of Ailsa Craig is the best known. The occurrences of Ailsa Craig and Mynydd Mawr, Carnarvonshire, are riebeckite-microgranites or paisanites. They contain ragged moss-like areas of riebeckite, together with microphenocrysts of quartz and alkalifelspar, in a microcrystalline groundmass of quartz and felspar. Riebeckite was also found by Dr. Teall in the granophyre of Meall Dearg and the neighbouring area of Druim an Eidhne, Skye. Harker described the riebeckite in these rocks as occurring in two forms, one having the usual ragged, sponge-like appearance, and the other being idiomorphic, the faces in the prism zone being well-defined, but with irregular terminations. The fourth occurrence differs somewhat from the others. This rock occurs as an intrusion into the Upper Old Red Sandstone, or Calciferous Sandstone of Easter Eildon Hill, Melrose, and was described by Barron as riebeckite-trachyte or phonolite. It consists principally of sanidine, occurring both as microphenocrysts and in the groundmass, with interstitial patches of riebeckite, and a little nepheline. Harker describes the rock as an orthophyre.