About a mile and a half to the east of Llandudno, forming the eastern boundary of Orme's Bay, a range of Mountain-limestone runs from the Little Orme's Head on the coast nearly to Conway, enclosing between it and the Great Orme's Head, to the west, a flat tract of ground, which appears to consist for the most part of Boulder-clay overlain by a more recent alluvium.

Essentially the pores of Megacystis are diplopores, for they are arranged in pairs. This is evident on the inner surface of a plate (E 16169, E 7671). Here each pore-pair lies in a shallow depression, and each pore again lies in a slight depression at the bottom of this (fig. 14). Compare Sinocystis yunnanensis (antea, p. 538).

A large basic sill intrudes the Shineton shale (Cambrian) at Maddocks Hill, east of the Wrekin, near Wellington, Shropshire. An old quarry exposes the contact and reveals that the shale close by has been recrystallized to a hard, compact hornfels, the intensity of alteration decreasing away from the contact. Thin sections show that the metamorphic effect was solely thermal, the rock having been completely recrystallized, and biotite having been generated under conditions of the amphibolite facies. The metamorphism is compared with that brought about by other basic hypabyssal intrusions.

I HAVE read with much interest Mr. Horace Brown's account in the GEOLOGICAL MAGAZINE for February, 1896, of the boring for water in the Trias at Stratford-on-Avon. In it he makes brief allusion to the sandstones in the Upper Keuper, and refers to Mr. Howell's statement of the occurrence of certain sandstones near Henley-in-Arden. He does not seem to be aware that similar sandstones are more or less widely spread over a considerable area in some parts of the Midlands, north and north-east of Henley and north-west of Warwick at a higher level, the highest point being 445 feet above the level of the sea. Many years ago I noticed some sandstone in Miss Phillips' park at Edstone not given in the Survey Map, and I informed my friend the late Professor Ramsay of the fact. These sandstones may also be seen in many places, especially in the parish of Rowington. They are exposed on the banks of the canal and along the road leading to Warwick, and were formerly obtained from quarries in the parish now long ago filled up, according to certain old documents in our parish chest, which gives an account of payments made for stone from this place, and our fine church and others in the neighbourhood and some old houses are built of it. When the Great Western Railway was made here a deep cutting through the sandstones was exposed along the line at Finwood in this parish; and lately they were detected when the new line to Henley was constructed. All the higher ridges in this district—they can hardly be called hills—are composed of the sandstones, the lower ground, where the marls and sandstones have been denuded, being formed of the red marls below. Sections are generally rare, as the stone is seldom employed except at Shrewley quarry near here, where the best section of the Upper Keuper beds are exposed. There are about two beds of useful stone: the upper one is inferior to the lower or bottom rock, which is a hard sandstone of some thickness and makes a good building stone, and is used by the Canal Company. This quarry is famous for many interesting fossils so scarce in the Trias, and is noted for the remains of fish, viz., Semionotus, Acrodus (spines and teeth), footprints of Labyrinthodon, and, the rarest of all, moulds of several species of mollusks, the only British locality where any shells have been found. I may add that the wells in the parish are fairly supplied with water from the sandstones, but it is hard and more or less charged with sulphates.

The subject of ‘pleochroic halos’ has become endowed with peculiar interest since Professor Joly suggested that they are due to the radio-activity of the inclusions round which they occur. On looking into such petrographical literature as I possess, it appears that very few precise observations have been made regarding these halos, and it has occurred to me, therefore, that some of my own notes on the subject may be of general interest.

Outcrops of Carboniferous Limestone were examined along the coast of North Wales around Penmon in Anglesey, and Great Orme's Head, Gloddaeth and Llanddulas in Caernarvonshire and Denbighshire.

Tectonic forces have folded, jointed and faulted the Limestone, but each area has reacted differently. The differences are discussed and the effects on the different limestone units illustrated.

Caledonian structures adjacent to the areas are briefly discussed. Variation in fold strike from north to east or south-east in the Carboniferous rocks is a reflection of the change in strike in the Lower Palaeozoic rocks, as is the northwest to north strike of the faults.

It is postulated that folding and faulting of the Carboniferous Limestone areas during the Hercynian orogeny was totally guided by Pre-Cambrian and Caledonian structural trends in Anglesey and on the mainland coast, and that the southern compression during the orogeny only accentuated pre-existing trends.

The following note is based on two papers by Professor A. G. Nathorst and on further details which he has kindly communicated by letter. For the loan of the block (Fig. 1) thanks are due to Dr. H. Munthe, Secretary of Geologiska Föreningen i Stockholm.

By the term ‘collodion imprint’ is meant the impression of any surface on a thin film of collodion. Such an impression is obtained by letting a drop or two of collodion dissolved in ether fall on the surface to be copied. The ether evaporates rapidly, so that in two or three minutes the film is hard. If it does not of its own accord come loose at the corners, it is easily raised by a needle or sharp knife. It is then lifted on to a glass microscope-slide and preserved dry under a cover-slip held in position by gummed strips of paper or by Canada balsam. When the imprint is very sharp, the film can, if desired, be preserved in glycerine-jelly without its distinctness being greatly affected. Some films may be less successful than others, and some may curl too much, so that it is as well to take more than one imprint. In any case it is advisable to throw away the first made, since it usually retains some dust from the surface of the object, whereas following films will be free from this. If the collodion solution is too thick it may be thinned by the addition of ether or of ether and alcohol.

Two valuable pamphlets on Jurassic Ammonites have lately appeared. One of these is entitled “Cephalopodes nouveaux ou peu connus des Étages jurassiques de Normandie, par Louis Brasil.” This author, who has paid very considerable and successful attention to the Jurassic rocks in the neighbourhood of Caen, describes and figures (there are four plates) nineteen new species of Ammonites belonging to fourteen genera, viz.: Lytoceras, Phylloceras, Catulloceras, Zurcheria, Dorsetensia, Bajocia, Pæcilomorphus, Hammatoceras, Erycites, Oppelia, Cadomoceras, Strigoceras, Cosmoceras, Œcotyphius. Of these genera one is new, namely, Bajocia, founded on an unique specimen; and it must be confessed that the example is sufficiently distinct in every way to warrant this treatment. Although the author does not say so, it is evident the genus belongs to the subfamily Sonniniæ and M. Brasil practically admits as much when he states that it is very near to Dorsetensia. He further says that he considers it to be a branch from Haplopleuroceras, whose representatives have lost not only the two rows of spines, but even the keel and the furrows. We find ourselves unable to agree with this opinion, because the periphery is rounded and flattened; in our experience the keel and furrows do not disappear without leaving some trace of their former existence on the configuration of the periphery. We agree with the author that Bajocia is near to Dorsetensia, and we are inclined to think it is a late-surviving example of the stock whence Dorsetensia originated, and a “cousin” of Zurcheria.

Lower Carboniferous strata are shown to be absent from the Amazon basin and Ghana, the Bermejo series of Bolivia is Permo-Triassic, the Sekondi series of Ghana does not include glacial deposits and may prove to be Devonian, early Carboniferous glaciation is unknown in Africa and restricted to Argentina in South America. In the light of these interpretations the extent to which late Carboniferous glaciation affected northern South America and Africa is briefly reviewed and shown to conflict with the reconstructions by L. C. King (1958). The non-glaciation of Africa and South America north of at least latitude 25 degrees South during early Carboniferous times is regarded as proving that these areas did not pass through the south polar region at that time. The known distribution of early and late Carboniferous glacial deposits is considered in relation to continental drift and movement can only have been westwards during the Carboniferous period.

Capping a small patch of London Clay on the highest part of Bostall Common (234 O.D.), there is a ‘drift’ that presents peculiarities identical with part of the gravel on Shooters Hill (2 miles distant) at 424 O.D.

In the year 1865 portions of the upper and lower jaws of a large extinct fish that had been found imbedded in the Globigerina Limestone of Malta were submitted by Dr. Leith Adams to Professor Owen for identification. Adams had considered them as being the remains of a crocodilian; but in a paper that appeared in the GEOLOGICAL MAGAZINE for April, 1865, Owen pronounced them to be the remains of a large extinct fish that belonged to “the cycloid order, and having sauroid dentition,” and he proposed that “this fine addition to Miocene Tertiary fishes” should be known by the name of Stereodon Melitensis.

A portion of the bony skeleton of a fish of the same species was also discovered in the same locality; but as it was not sent with the other specimens, it has been neither figured nor described.

It is remarkable that in English geological literature and in our Universities so little attention is given to this important branch of geology. Probably it is because in this country petroleum occurs only in small quantity; nevertheless, in many parts of the British Empire petroleum mining has become a great and increasing industry, and is one of the chief directions in which geology is of practical use to-day. The writer therefore hopes that an orderly summary of present knowledge may be useful.

After he had published his account of the geology of the Solomon Islands, Dr. Guppy was good enough to present to the Museum of Practical Geology a series of typical specimens showing the chief varieties of calcareous and argillaceous deposits met with in the islands. This collection includes rocks, washings, picked organisms, with a few microscopic slides, and it constitutes a series very valuable for reference.