Geologists and archæologists are much indebted to Professors Osborn and Obermaier for useful up-to-date summaries of our knowledge of early man, with extensive bibliographies which include most of the latest papers. So much progress has heen made in the study of the subject during recent years—especially since the Prince of Monaco's foundation of the Institute of Human Palæontology in Paris—that synoptical treatises of this kind are an indispensable aid to further advance. Both are also intended, with their beautiful illustrations, to arouse interest in a much wider circle than that of students who are actually engaged in research. They should, indeed, help in urging the educated public to take every opportunity of bringing to the notice of scientific men such casual discoveries of human remains and traces of human handiwork as they happen to meet with. It is lamentable to think how few of these discoveries, even under existing circumstances, are rescued from destruction and made available for study.

It may interest readers of the Geological Magazine to have a summarized account of the new data obtained regarding the Post-Eocene and Post-Miocene movements in the Gulf of Suez area, and notably in its southern portion, the oilfield region of Egypt (see Map, Fig. 1).

The Javan fossil corals collected by the Austrian frigate Novara included a specimen on which Reuss (1866, p. 172) founded a new genus, Polysolenia. He described it (ibid., p. 172) as showing in the structure of its cœnenchyma “eine überraschende Ähnlichkeit mit Polytremacis und Heliopora”. “Das Cönenchym besteht aus langen, ziemlich dicken, geraden, neben einander liegenden Röhren.” These tubes, according to his account, occur in circles of six around a central tube. Reuss repeated (p. 174) that the cœnenchyma is composed of regular parallel tubes (Röhren), whereby it is closely allied to Heliopora and Polytremacis. He named it Polysolenia “nach ihrer röhrigen Structur”. Reuss' illustrations suggested some suspicion as to the accuracy of his description, since the dark parts of his figures might be interpreted as the original solid structures of the coral, and the light parts as the matrix. If so, the cœnenchyma would be trabecular and the septa a series of thin lamella. Reuss, however, was emphatic that the septa are thicker than the walls of the supposed cœnenchymal canals; and, if so, the light parts of the figure represent the original solid structures. If the coral had undergone a double change in fossilization Reuss' view was possible; and his statements that the circular rods are casts of canals were so positive that, though in 1900 I mentioned my doubts, I felt bound to dismiss them. So I accepted the fossil as a Miocene Helioporid, and as the name Polysolenia was preoccupied renamed the genus Octotremacis (1900, p. 302).

The existence of two ridges of Pre-Cambrian rocks in South-West Carnarvonshire is well known. The more northerly of these ridges extends from near Bangor to Carnarvon, a distance of just over 8 miles. It runs in a south-westerly direction, close to and parallel with the Menai Straits, and terminates at the hill called Twthill—a prominent feature in the town of Carnarvon. The more southerly ridge—commonly known as the St. Annes–Llanllyfni ridge—stretches from St. Annes in the Nant-Ffrancon Valley to the village of Llanllyfni in the Nantlle Valley. This ridge is 12 miles long and has a south-westerly trend; it is therefore roughly parallel to the Carnarvon-Bangor ridge, from which it is distant about 2 miles. It is with the area at the south-west end of the St. Annes–Llanllyfni ridge that the following remarks are concerned. The object of my

investigation has been to establish the succession of rocks in this area, and to correlate it, if possible, with the main portion of the ridge lying to the north-east. The results are set out in detail in the following pages. Text-map I shows the position of these two Pre-Cambrian ridges and also the extent of the area to be considered in detail.

To the student of Cambrian geology, the writings of C. D. Walcott are always matters of enlightening study, not only for the matter they contain but also because they combine that admixture of stratigraphy and palæontology in which the latter, though accorded a prominent position, is always used to the full to subserve the wider claims of the former.