The chemical evidence with relation to the formation of a laterite from a diabase was given in a paper in the March number of the GeologicalMagazine, pp. 120–3. Since that account was written I have made microscopical examinations of the materials therein described.

1. The raised beach near Porth Clais consists of shingle and large wave-worn boulders resting on a rock-platform, and overlain by angular head or rubble of local rocks.

2. Glacial drift (Boulder-clay) overlies the head at the western end of the section, and towards the east has ploughed into the raised beach and rests on the solid rock. Some of the boulders of the raised beach and a small piece of the rock-platform are definitely striated under the Glacial drift.

3. The raised beach is pre-Glacial in the sense that it underlies the Glacial deposit.

4. The raised beach contains non-local boulders which may have been transported by drifting shore-ice.

In the course of the preparation of the second part of the Catalogue of the Marine Reptiles of the Oxford Clay in the Collection at the British Museum, it has been necessary to examine in detail the structure of the skull and mandible of the Pliosaurs, especially of Peloneustes philarchus, several excellent specimens of which are included in the Leeds Collection. In the course of this examination several peculiarities have been observed, which on the one hand tend to reconcile the conflicting views as to the structure of the skull roof that have been put forward, and on the other serve to correct the interpretation of the elements of the mandible given in the first part of the Catalogue.

After I had forwarded the paper on “The Residual Earths of British Guiana commonly termed ‘Laterite’”, published on pp. 439–52, 488–95, and 553–62 of the GeologicalMagazine for October, November, and December, 1910, I visited the neighbourhood of Christianburgh and Akyma on the Demerara River in British Guiana and examined a small long-deserted quarry in a very fine-grained diabase intrusive in hornblende - granitite - gneiss near the latter pluce. I obtained from the lateritic earth lying on the mass of unaltered diabase a boulder of that rook in which the central parts were ideally fresh, whilst the outer parts were decomposed into laterite. I separated these parts with great care into an outer red one, apparently an ordinary ferruginous laterite, and an inner one, buff-coloured with whitish spots in it, which was in actual contact with the unaltered rock. When I obtained the boulder these crusts were quite soft, but after a few days' exposure to the air they hardened considerably.

The following note on the rocks of the shore-line of part of the Gold Coast Colony are a result of a short journey I undertook there in 1910. On that occasion I landed at Cape Coast Castle and travelled westward, staying successively at Elmina, Chama, and Sekondi.

Various forms of Macrourous Decapod Crustacea referable to the genus Eryon have attracted my attention from an early date, and in the GeologicalMagazine for 1888 I gave a summary of all the then known species.

Non-marine Mollusca are extremely rare in the Pliocene deposits of this country, which fact must always be a matter of regret to the Palæontologist, since they are of the utmost importance in connexion with the origin of our present fauna. Unfortunately, in addition to their rarity, they are often decorticated or fragmentary, whence no doubt the differences in opinion as to their correct determination. A re-examination of all the available material has convinced us that there is still much to be done before it will be possible to reach finality. In these matters so much depends on one's standpoint. If one starts with the preconceived idea that the Pliocene shells must be identical with the recent forms, it is easy enough to identify them, even if one has to go to Japan or Greenland to find its present habitat. If, on the other hand, one considers it better to study carefully the results of recent work on other branches of the fauna, it is obvious that different results will be arrived at. Hence we are quite prepared for any differences of opinion as to the correctness of our views or the wisdom of creating four new species, as we now venture to do.

In the year 1866 Hicks and Salter recorded the occurrence of certain rocks in the neighbourhood of St. David's which they regarded as Tremadoc deposits. The beds appeared to them to rest conformably on the Lingula Flags, but when the rocks were compared with those of the Tremadoc area striking lithological differences were noticed. Accompanying the report was a list of fossils collected from the beds, and the fauna was so wholly unlike that of the North Wales deposits that the authors were led to conclude that the dissimilarity was due to the conditions under which the strata were deposited.

Detrital Laterite or Lateritite.—Many of the so-called low-level laterites and some of the high-level laterites consist of admixtures of detritus from the various varieties of laterite already mentioned, with quartz and argillaceous detritus from granites and gneisses, the whole cemented together by the action of water on the lateritic constituents of the mixture. For such rocks the name detrital laterite is available, and could be used in all cases in which the reconstructed rock contained, say, at least 40 per cent of lateritic constituents. Theoretically, detrital laterites may contain, as an upper limit, 100 per cent of lateritic constituents, corresponding to the case of a detrital rock composed entirely of fragments of a pure laterite, without admixture of extraneous constituents. From the above it will be seen that I would allow greater elasticity in using the term laterite for the detrital forms than for those formed in situ (see next paragraph), provided the adjective detrital be carefully prefixed; for this word seems to me to imply the great variability of composition that must characterize these secondary laterites. But if it were considered desirable to avoid the use of the word laterite altogether in this connexion, the obvious term to use instead would seem to be lateritite, implying a rock the individual constituents of which are pieces of laterite. This term would be of great utility, and could be applied to all detrital and reconstructed lateritic rocks. The word is put forward here merely as a suggestion, but if geologists were to distinguish, in writing, between laterite, lateritoid, and lateritite, great clarity could be introduced into the literature of these substances.

1. The term laterite is used in two ways, namely, stratigraphically as the name of a geological formation, and petrographically as the name of a tropical superficial rock. This discussion relates only to the use of the term as a rock name.

2. Laterite (or rather some varieties of it) is formed by a process, the modus operandi of which is not discussed here, by which certain rocks undergo superficial decomposition, with the removal in solution of combined silica, lime, magnesia, soda, and potash, and with the residual accumulation, assisted, no doubt, by capillary action, metasomatic replacement, and segregative changes of a hydrated mixture of oxides of iron, aluminium, and titanium, with, more rarely, manganese. These oxides and hydroxides of iron, aluminium, titanium, and manganese are designated the lateritic constituents.

3. This residual rock is true laterite, and the presence of any considerable proportion (> x10 per cent) of non-lateritic constituents requires expression in the mime, as it always indicates want of completion in the process of lateritization. True laterite contains, then, 90 to 100 per cent of lateritic constituents.

Some years ago the British Museum acquired from Dr. William Clark a collection of the remarkable Arthrodira found by him in the Upper Devonian shales of Ohio. In this material there are several specimens which were described as new before being brought to Europe, but concerning which there has been more or less doubt among students of the Arthrodira. Hitherto, however, it has been quite impossible to dispel this doubt since the material necessary to a comparative study of the forms in question is to be found only in America. Last year I enjoyed the privilege of going over this material in the British Museum, thanks to the courtesies extended to me by Dr. Arthur Smith Woodward, F.R.S., the Keeper of Geology, and as I had just come from a study of the American forms I was in a position to resolve these doubtful cases. The results of this study are presented in the following pages.

That curious fossil organism, long known as the ‘Dragon-tree’, has been a puzzle to palæobotanists for almost three-quarters of a century. Bandied about among various monocotyledonous genera, then thought to be possibly related to the Cycads, and finally given a non-committal name that was without implication of kinship, though placed among the Cycads, it has at last, through the admirable research of Dr. M. C. Stopes, been definitely allocated among the Conifers, and even among the higher members of that group. Dr. Stopes is certainly to be congratulated for having worked out its affinities in such a conclusive and convincing manner. It is to be regretted, however, that the scientific name she has finally adopted for the ‘Dragon-tree’ is not the one that is likely to meet the requirements of nomenclatorial permanency. The nomenclature of systematic palæobotany does not differ essentially from that of livmg plants, and must abide by the same rules.

Although the remains of pedunculated Cirripedes are comparatively rare in the Chalk of England, especially in its lower zones, one can, by careful collecting extended over a number of years, get together a fair series of the detached valves of the capitulum. Thus a very fine series of Cirripede remains has been accumulated by Dr. H. P. Blackmore, F.G.S., from the upper zones of the Chalk near Salisbury. This collection, which, through the kindness of Dr. Blackmore, I have lately had the opportunity of examining, is especially rich in the valves of Scalpellum fossula, Darwin, and S. maximum (J. de C. Sowerby).

The question as to the existence and characters of the jaws in Conulus albogalerus, Leske, has long been a subject of controversy. On prima facie evidence it seemed probable, so long as the genus was retained among the Holectypoida (the Galeritidæ of older authors), that jaws existed. Conulus appears as a successor to Discoidea among the Cretaceous Echinoids, and, with a few exceptions, all echinologists admitted that the latter genus was armed with a lantern and teeth. The truth of this assumption was proved by Lovén (Lovén, 1892, p. 53), and the details of the jaw structure were elaborated recently by myself in this Magazine (pp. 148–52, PL VI, 1909). That Conulus should be classed among the Holectypoida seems to be an established proposition, and it appeared in the early part of the Cretaceous period, together with Pyrina, probably as an offshoot from the Holectypus line of descent.

The more exact investigation of the distribution and mode of occurrence of Neolithic remains has received a much needed stimulus from the publication of Professor Brögger's memoir dealing with the position of the strandlines in South-Eastern Norway during the stone age of that country. It has been clearly demonstrated in this important work that it is possible to distinguish, even in the relatively short-lived Neolithic culture, certain phases of chronological value, and to correlate these phases, by means of the distribution of the implements which characterize them, with the successive stages in the elevation of the land which affected Scandinavia in postglacial times. It has become clear, therefore, that the careful registration and description of Neolithic relics may lead to the most important scientific results, and it will be realized by all who indulge in archæological collecting that an exact determination of the locality of any find and of the relations it bears to the superficial deposits of the neighbourhood, more especially to the old shorelines which border the coasts of the British Isles, is of the utmost importance.

In the course of working through the large collection of Coal-measure fossils in the Manchester Museum I have recently discovered a number of interesting, and hitherto unrecorded, forms from the well-known ‘Marine Band’ in the Middle Coal-measures of Ashton-under-Lyne. The most interesting of these additions is undoubtedly Archæocidaris, a genus which is not at all common in the Coal-measures of this country, though fairly abundant in North America. Hitherto it has only been recorded from the North and South Staffordshire Coal-fields; its discovery, therefore, at Ashton constitutes the third record for the British Isles.

The latest book on metamorphism, Dr. V. Grubenmann's Kristallinen Schiefer, still leaves it an open question what a metamorphic rock is. Generally speaking there is no doubt about the matter; every geologist has a more or less precise idea of what he means by the term, but no one has yet been able to propound a definition which is perfectly satisfactory, and which will enable one to distinguish a metamorphic rock from all other kinds and at the same time convey an expression of the characteristic peculiarities inherent in such a rock. The need of a definition is very necessary. The want of it has led Dr. Grubenmann to include some rocks among the crystalline schists which one ordinarily would not refer to that class, and on the other hand there are some rocks frequently referred to that class which are not included. In the first case, the masses of emery form the twelfth group of Dr. Grubenmann's classification, yet the analysis of the Naxos emery, which reveals traces of boric oxide (1.15 per cent. in one case) would seem to place these lenses among the ore-bodies deposited by pneumatolitic action.