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.

Professor Patrick Marshall's important and interesting memoir, which has recently appeared, on the geology of Mangaia, one of the Cook Islands, inevitably suggests a comparison between this island and Rurutu in the Austral Group, which I visited in 1925, during the St. George Expedition to the Pacific, and described in a recent communication to the Geological Society. Owing to the shortness of the Expedition's stay at this island, my observations were necessarily somewhat incomplete, but I had the advantage of many conversations with Mr. S. Russell, who spent several months there in 1924, prospecting for minerals. He gave me copies of his reports, and he accompanied us on our visit.

In their memoir on the Cauldron Subsidence of Glencoe, the authors, Messrs. Bailey, Clough, and Maufe, showed that the structure owes its origin to a cylinder that has sunk; around the edges there are various crush phenomena, culminating in fusion and actual lava. Alongside Glencoe is the granite mountain of Glen Etive, defined by a circular fault, and thus representing a cylinder that has been pushed up. The authors discuss the bearing of their work on general questions of geology; they show that the cylinder may simply sink, and the top be covered with the rocks originally in place upon it. Branca described a similar case in the Ries in Swabia. In others the circular fault has served as the orifice from which lava has been poured over the floor of the pit, as in the Hegau.

In 1915 I published a short paper in which it was shown that the Coal Measures of the Clapton area on the northern side of the Clifton-Clevedon ridge, Somerset, rested with strong unconformity upon the Carboniferous Limestone and all older rocks. Subsequently Professor S. H. Reynolds, having observed the relations at Court Hill, Clevedon, where the Carboniferous Limestone is clearly thrust over the Coal Measures, saw no reason to differ from the earlier observers, Buckland and Conybeare, the officers of the Geological Survey, and Lloyd Morgan, all of whom regarded the Main Limestone-Coal Measures junction south of Clapton as a faulted one; accordingly, on the map accompanying his paper, Professor Reynolds showed the boundary as a fault as far as the eastern limit of the Coal Measures, even where they transgress from the Main Limestone across the Lower Limestone Shales. At a later date Dr. E. Greenly, in a description of the sections at East Clevedon Gap, about three miles west of Clapton, referred to the unconformity as follows: “Whether, as believed by A. Vaughan and F. Dixey, there be unconformity, the whole of the Visean, with apparently the Lower Coal Measures as well, having been locally removed by inter-Carboniferous erosion, is a question that will not be discussed in this paper. But, independently of that question, there is reason to suspect that the base is cut out, for the lowest visible sandstones on the wooded bluffs are buckling over, as if driven forward on a thrust-plane. Should serious unconformity be eventually proved, this thrust need not be of much tectonic importance. In any case, the plane, whatever its nature, is over-stepped by the Bella-Vista Thrust-plane…”

Very little is known of the early history of the non-marine Gastropoda; hence the discovery in the coal-bearing strata of Scremerston (Northumberland) of a small species closely resembling certain modern fluviatile operculate shells is of considerable interest. My thanks are due to Mr. J. Pringle for bringing the specimens in question to my notice; to Mr. R. G. Carruthers, to whom their discovery is due, for sending me particulars; and to Dr. F. L. Kitchin for permission to borrow them from the Museum of Practical Geology, where they are deposited.

IN 1924 I drew attention to the presence of a coarse-grained conglomerate at the base of the Gebel Moqattam, near Kait Bey. This paper contains a detailed description of the occurrence, of which at the same time I shall endeavour to determine the strati-graphical significance.

The method attempted of correlation of plutonic masses by their accessory minerals is successful, and particularly so with the acid rocks. The results effected in the Channel Islands are as follows:—

1. Confirmation of the existence of granites of two ages in Jersey, and correlation of the Fort Regent and Gorey masses for the first time.

2. Correlation of the Cobo Granite of Guernsey with the “Older” Granite of Jersey (Gorey and Fort Regent).

3. Conclusive evidence to show that the Cobo Granite is the last stage of the Differentiation Series of North Guernsey, previously thought improbable.

4. The probable occurrence of both “Newer” and “Older” Granites in Alderney, making a Pre-Cambrian age for the “Newer” Granite highly probable.

5. The dissimilarity of the heavy residue of the “Newer” Granite to that of the Dartmoor Granite.

6. The similarity of the residue of the “Older” Granite with that of the Granite Gneiss of the Lizard and their suggested correlation.

7. The individuality of the gneisses of South Guernsey.

8. The occurrence in hybrid rocks of the mineral suites (particularly the zircons) of both rocks involved, consequently we have here a new method of demonstrating the hybrid nature of a rock.

Many rocks previously termed diorites in Jersey, Guernsey, and Alderney are shown petrographically not to be true diorites, some being gabbros, others hybrids.

The occurrence of acid-soused basic rocks in Jersey, Guernsey, and Alderney is pointed out, and their petrography described.

The occurrence of amphibolites in Roselle Bay, Alderney, is made known for the first time, and their petrography described.

In the course of the whole work sixty-three rock specimens have been crushed and passed through bromoform according to the method of procedure previously outlined, making an aggregate of about 15 lb. of rock crushed. From this crushed rock nearly four hundred slides of grains have been prepared, and of these about 90 per cent are nonmagnetic. In addition eighteen thin sections have been prepared.

I wish to thank Mr. A. E. Mourant, B.A., for some of the specimens of gneisses from southern Guernsey, and also Dr. G. H. Plymen for the specimens from Alderney. The rest of the material. was collected by myself.