Beds of shale, sandstone and conglomerate containing Upper Cretaceous fossils occur at several places in Jamaica, and in every instance that I know of they are found to be more or less in close association with Rudist limestones. They generally occur below the limestones with Rudistae but in at least one locality, that at St. Ann's Great River, fossiliferous shales occur immediately above and also a considerable distance, 1,000 feet or so, below a bed of Rudist limestone.

This important earthquake is chiefly of interest on account of its connexion with the strong Hereford earthquakes of 6th October, 1863, 30th October, 1868, and 17th December, 1896. At least three of the four earthquakes (those of 1863, 1896, and 1926) seem to have originated in the same twin-foci, the epicentre of one lying near Hereford and that of the other near Ross. The fourth earthquake (that of 1868) originated in the Ross focus, possibly also in the Hereford focus.

1. The Dent Fault diminishes in throw towards the north, and is almost non-existent 3 miles south of Kirkby Stephen.

2. The principal line of dislocation is then displaced about a mile to the east, where there is a steep monoclinal fold, replaced sometimes by a fault, running in a direction parallel to the Dent Fault and also having a downthrow to the east.

3. Further parallel faults, many of them hitherto unmapped, assist in the subsidence of the country to the east.

4. Cross-faults, in most cases with downthrow to the south, accommodate the margin of the “Rigid Block” to local increase or decrease of throw.

5. These two systems of faults are of approximately the same age, and were brought about by the same crustal movements.

In 1925 my friend Mr. M. P. Latter published in this magazine a short paper on the rocks in the neighbourhood of Cardigan. I was interested in these rocks at the time he was working on them, and in his absence abroad I have recently paid a few brief visits to this region; and it may be desirable to place on record such supplementary facts and inferences as have been obtained.

Many travellers in Western China have remarked the presence of ancient moraines long since severed from the glaciers which made them, of glacial lakes, ice-worn valleys, perched blocks, and other relics of glaciation. Throughout the Tibetan Marches, in the provinces of Szechuan and Yunnan, such evidence is abundant. Even on the southern face of the Himalaya, where very large glaciers exist, Hooker showed that the ice once extended over a much greater area.

A Porose corals have, with few exceptions, received little attention in Britain since the publication of works by P. M. Duncan and R. F. Tomes, during the latter half of last centary. The newer methods of investigation by means of thin slices and serial sectioning, so successfully employed by Drs. Stanley Smith and W. D. Lang, and others, in the Rugosa, were not then in use, and so very little is known of the internal structures–the only basis for classification and comparison–or of the developmental stages of the Aporosa.

Professor Holmes's further article, substantiating points questioned by me, may be divided into two parts. In the first he gives a statement of some geological phenomena not yet explained in accordance with his old theory of the earth's thermal history. In the second he maintains that these demand the abandonment of the theory and its replacement by a new one, which I consider qalitatively wrong. With regard to the first part, I consider that Professor Holmes has done a great service to geophysics in bringing these points forward in so clear a way. It has never been claimed that the old theory explained everything, and in some points it certainly requires to be supplemented; the questions at issue are what modifications are required, and whether they are such as to change the whole character of the earth's thermal history. But before problems can be solved it is necessary that they should be stated, which is liable to be at least as difficult.

The internal structures and development of the genus Holocystis Ed. and Haime, of which only one species, the type, has been recorded, have not previously been described. It is the purpose of this paper to repair the omission. This Aporose genus is interesting in that it exhibits certain characters normally well developed amongst Rugosa and in possessing four principal septa arranged in a cruciform manner within the calice, instead of having its septa merely arranged on the hexameral plan characteristic of normal Aporosa. I am greatly indebted to Dr. Stanley Smith for the loan of certain specimens, and for much helpful criticism and advice, and to Professor S. H. Reynolds for access to, and use of, material in the geological collections of the University of Bristol.

The pebble about to be described was found in the Middle Louth Seam at Swannington Colliery, near Ashby-de-la-Zouche, in Leicestershire, and was presented to the writer in the year 1899 by the late Mr. Henry Copson Peake, who at that time was manager of the Swannington Colliery and also general manager of the Walsall Wood Collieries, near Walsall.

As a result of work on the Chalk Rock in the Hitchin district during the last two years, I have obtained several Ammonoidea which differ in certain respects from those already figured and described and include two new species.

The Geological Magazine did me the honour in 1914 to publish a paper in which I proposed a classification of eruptive rocks on the basis of the “degree of saturation” of the constituent minerals with silica. Any mineral which is proved by its field associations to be stable in the presence of free silica, under such conditions as prevail in natural rock magmas, was said to be “saturated” with regard to silica. Other minerals, such as leucite and olivine, which are not stable in presence of free silica, within the ordinary range of magmatic temperatures, were said to be “unsaturated” with regard to silica. Eruptive rocks were then classified as “oversaturated”, if they contained quartz or tridymite; “under-saturated”, if they contained any unsaturated minerals; and “saturated” if neither free silica nor any unsaturated mineral was present.

(a) The insoluble residues from the limestones contain detrital quartz, amorphous, cryptocrystalline and microcrystalline silica, siliceous pseudomorphs after organic remains, sponge spicules, fluor, magnetite, pyrites, zircon, ilmenite, tourmaline, muscovite, biotite, and felspar.

(b) No megascopic chert occurs.

(c) The succession contains more arenaceous and argillaceous rocks than occur in the Avon section. They contain magnetite, rutile, zircon, ilmenite, tourmaline, muscovite, and staurolite among the rarer constituents

(d) Oolites have a notably small average percentage of insoluble residues, probably owing to their rapid formation, in clear water.

(e) The detrital material in the Avonian rocks of Sodbury has probably been derived, directly or indirectly, from some Pre-cambrian complex to the north or north-west.

This quarry is situated three-quarters of a mile north-east of Arundel Castle on the west bank of the River Arun.

Mr. E. J. Wayland, of the Geological Survey of Uganda, has recently found three interesting fossils which throw further light on the age of the beds to the west and north of Mombasa. One of them is a cast of an ammonite in brown ironstone, which has been kindly examined by Dr. L. F. Spath; he says that being only a cast its specific identification is perhaps impossible. It is a Grossouvria, and he says it is very similar to several examples of G. lateralis (Waagen), from the Callovian anceps beds of Kachh. He identifies it as certainly a member of Siemiradzki's form-series of Perisphinctes balinensis, Neumayr. This identification is of interest as the fossil was obtained at the point 10/6 miles from Mombasa on the Uganda Railway. This position lies to the west of, and therefore at a lower horizon than, the ammonite-bearing shales near Mombasa. At 11 1/9 miles along the railway I found a lamellibranch in some dark shales and Dacqué (Geol. Rundsch., vol. i, 1910, p. 159) has recorded from near by some obscure Cephalopod and plant remains which he identified as Bathonian.

Only a single crab (Carcineretes woolucotti Withers, Ann. May. Nat. Hist., ser. ix, vol. x, 1922, p. 535, pls. xvi, xvii; vol. xiii, 1924, p. 91, pl. iv, figs. 1–4) has so far been described from the Cretaceous rocks of Jamaica. Remains of this crab have been found in the upper part of the Rudist Limestone both at Logie Green and Trout Hall, near the Rio Minho River, Central Jamaica. Dr. C. T. Trechmann, F.G.S., has now discovered a second species of crab, Ranina trechmanni n. sp., and this was found in the shales some 40 feet below the Rudist Limestone between Cambridge and Catadupa, West Central Jamaica. The Rudist Limestone is considered by Dr. Trechmann (Geol. Mag., Vol. LIX, 1922, p. 505; Vol. LX, 1923, p. 345; Vol. LXI, 1924, p. 393) to be of Maestrichtian age, and the shales below, in which the present crab occurs, to be Campanian. This conclusion is borne out by, and to a great extent based on, the evidence of the Cephalopods described by Dr. L. F. Spath (Geol. Mag., Vol. LXII, 1924, p. 28) from the shales underlying the Rudist Limestone at Providence, Port Antonio, Eastern Jamaica, and considered by him to be of Upper Senonian and Maestrichtian age. Professor H. L. Hawkins, however, from a study of the Echinoids (Geol. Mag., Vol. LX, 1923, p. 215) does not agree that these rocks are so high in the Cretaceous as the Campanian or Maestrichtian, and considers that they have a time range from the base of the Upper Cretaceous to about the base of the Senonian.