The object of this preliminary note is to inquire how far the marine mollusca can be used in correlating the Quaternary marine deposits in Britain.

The peculiar coral to be described below was collected by Mr. R. S. Allan, of New Zealand, at Yass, New South Wales. It has a superficial resemblance to Favosites but close examination shows it to be imperforate and to belong to the Chaetetidae. It shows so many characters of interest that it seems to merit a full description.

Mr. J. V. Harrison, B.Sc., has recently collected some coral limestones from two localities in Venezuela, which he has entrusted to me for identification and description. The corals indicate the existence in eastern Venezuela of a rich fauna, for the specimens include fragments of seven genera. Some of the corals are too small for specific, and some for certain generic determination but as there appears no likelihood of further material being collected, it seems advisable to describe what is available to direct attention to an interesting and varied coral fauna. The two localities represented are Port Piritu, on the shore of the great bay west of the town of Barcelona in eastern Venezuela, and Punceres to the west of the Gulf of Paria between the two branches of the Rio San Juan and due west of the lower course of that river. A map, for which I am indebted to the Anglo-Persian Oil Co., through Mr. S. Lister James, shows that the position of Punceres is at about 10° N., 631/2° W. The corals were collected during surveys made for that Company, which has paid for the accompanying plate.

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 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.

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.

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.

In the present note it is intended to record a find of considerable importance to geologists and palaeogeographers, namely the discovery, last summer, by Mr. J. M. Wordie, St. John's College, Cambridge, of Lower Eotriassic ammonites at three localities on the south side of Gael Hamkes Bay, on the East Coast of Greenland, in 74° N. latitude. There are altogether ninety-five specimens, most of them well preserved, including various new forms, of which I hope to publish full descriptions elsewhere.