Much attention has been paid to composite dykes and sills during the present century, and accepted definitions of the term “composite” centre about that of Daly (1933), who has stated that composite dykes are formed by successive injection of chemically differing melts into the same fissure which widens to receive them.

At a distance of about two and a half miles from Aberystwyth, the road leading eastwards towards Devil's Bridge curves round the north side of a small knoll on the ridge separating the larger valley of the Rheidol on the north from the smaller valley of the Paith on the south. The road here reaches a height of 400 feet and the knoll rises a further 100 feet above it. Opening directly from the south side of the road, a quarry (now disused) has been excavated in the knoll and in this quarry the Aberystwyth Grits present a very striking appearance, showing a zig-zag structure with one fold above the other.

The aim of this paper is to present a brief description of the field relations of the South-West Granite Complex in the Island of Jersey, as shown by recent field work, together with a short description of the granites themselves. The area to be described forms a dissected peneplain, probably of Pliocene age. The magnificent coastal sections from St. Aubin to La Carrière reveal the nature of the two granite intrusions, the first into Pre-Cambrian shales, which are found to the north and north-east of the area; and the second a newer granite intrusion into the older one. Inland, the scenery is less spectacular, but the path from St. Aubin to Corbiére, which follows the old railway track, contains many excellent exposures of granite and shales, together with granite-shale contacts in the valley west of St. Aubin. West of Pont Marquet it traverses open country with dune sand encroaching from St. Ouen's Bay.

Facies change and lithological variation traceable in the outcrop of the Permocarboniferous rocks exposed over portions of some 1,400 square miles of jungle country in north-west Pahang and south-west Kelantan are outlined in this paper. The area, some 70 miles N.–S. and 10 to 25 miles E.–W., is bounded by the 101° 45′ E. meridian in the west and by the Gunong Tahan and Gunong Benom Ranges in the east (Text-fig. 1A). The territory described lies mostly in Ulu Pahang of which a reconnaissance map, scale 8 miles to an inch, and a memoir have been published by Scrivenor (1911). Between 1937 and 1941 the 1,200 square miles lying between meridians 101° 45′E. and 102° 00′E. have been mapped partly on the scale of 1½ inches and partly 2 inches to a mile. The geology of the southernmost 300 square miles (Sheet 3 B/4, Raub) has been described by Willbourn (A.R., 1933–34) and the writer (1939); interim reports on the 300 miles (Sheets 2 N/16, Benta, and 2 O/13, Lipis) immediately north have been published by Service (A.R., 1938–1940), and of the northern 600 square miles (Sheets 2 N/12, Chegar Perah, and 2 N/8, Merapoh) by the writer (A.R., 1937–1940; 1946).

Robert Etheridge, Jnr. (1874a, p. 310), records that the same species of Spirorbis as that in the Lesmahgow Silurian occurs in the North Esk section. The D. J. Brown collection with the specimens referred to is missing at the Royal Scottish Museum; but it would be interesting to know how closely these specimens compare with S. lewisii J. de C. Sowerby from the English Wenlock and Ludlow.

During 1931–4 several hundred specimens of these two species were collected, including a quantity of excellently preserved silicified material from an exposure of the Dayia Shales (Elles and Slater, 1906, pp. 197 and 198), near Norton in Shropshire. Serial sections and development of the material have made possible the detailed descriptions which follow.