A small collection of fossils from the Upper Ordovician of Quarrel Hill, Girvan, made recently by Mr. James L. Begg, is remarkable for the number and character of the lamellibranchs, several of which appear to be new. Their affinities are chiefly with those of the Ordovician of the United States and are consequently of special interest.

The determination of the true order of crystallization of minerals in a plutonic intrusion is not an easy matter, but a good deal of information on the subject may be obtained if such an intrusion shows a chilled edge or if there are dykes of corresponding composition. Fortunately, some of the Caledonian plutonic rocks of Western Scotland which we are about to consider do show chilled margins, and there is a series of dyke rocks, loosely termed porphyrites and quartz-porphyries, covering practically the whole range of composition for the rocks on the assumed liquid line of descent.1 It has been possible to study large collections of these housed in the Geological Department of Manchester University and in the Department of Mineralogy and Petrology, Cambridge.

The evidence relating to the problems raised by the Arenaceous Formation of the Main Range Foothills may be summarized thus:—

(i) The Foothills are built as a rule of predominantly arenaceous sediments; belts of quartzite-conglomerate occur and argillaceous types generally are interspersed with the coarser grained rocks.

(ii) Lithological variations northwards and southwards along the strike of the Formation, and eastwards and westwards through its strati-graphical succession are very great.

(iii) No fossils have been found anywhere in these rocks and their age is consequently not definitely known.

(iv) The Foothills have obviously been the site of orogenic pressures and metamorphism, and they appear to have formed a buttress against which the Permocarboniferous rocks have been moulded by forces from east-south-east or east.

(v) There is a persistent difference of 10° to 20° between the general strike of the Foothills Formation and that of the Permocarboniferous Formation along the eastern margin of the Foothills in the 35-mile tract examined by the writer. This fact cannot be accepted as proof that an angular unconformity exists because structural complexities dependent upon (iv) above can also afford a satisfactory explanation of this divergence of strike.

(vi) Scrivenor has mapped the Foothills Formation as Triassic, so that its easterly dip below the Permocarboniferous must, on this hypothesis, be due to overfolding.

(vii) Between the western margin of the Foothills and the Main Range granite, occur rocks, many of them strongly metamorphosed, which may originally have been calcareous shales, pyroclasts, and impure limestones, presumed, on lithological grounds, to be of Permocarboniferous age. Their alteration has been so profound that no transitional types have been discovered between thorough-going amphibole- and epidote-schists and the presumed parental calcareous sediments. Metamorphosed argillaceous and arenaceous rocks accompany them.

The rocks of the Wirral Peninsula in Cheshire were originally described by John Cunningham in 1839, as three series, two moderately resistant to the east and the west, separated by a central region of soft sandstones and marls, dipping uniformly eastwards. G. H. Morton noted this in 1872, as a good description of the strata, ignoring faults, and pointed out the significance of the faulting. Since that date the faults have been mapped in great detail, and most of the structural features ascribed to them. G. H. Morton was particularly accurate with his mapping of faults both in Liverpool (1899), and in Storeton (G. H. Morton, 1883, and H. C. Beasley, 1914). The folding finds its first mention in the Geological Survey Memoir of 1923, two elongated synclines being mentioned, one from Heswall northwards and the other from Storeton to Prenton. The former is undoubtedly an important synclinal feature, but the latter is made up of two folds, a north to south anticline at Storeton, and an east to west syncline at Prenton. The only other records of folding in Wirral are by F. T. Maidwell in 1920 and by T. A. Jones in 1937, who mention an anticline at Ellesmere Port. This paper is therefore chiefly devoted to a description of the folding in the area.

Nearly thirty-three years ago, in September, 1913, I searched the Harlech Grits for pebbles of the Mona Complex; and the search was a success: I obtained quite enough for a decisive demonstration. Still, their numbers were not great, and to obtain them had needed persistence; the search, indeed, occupied fully a fortnight. I sought a reason at the time in the horizons from which they came, for they were not from the Cambrian base. We shall presently discern a far more cogent reason: between the Cambrian and the Complex there is more than one formation. The surprise is not in their moderate numbers, but rather that there were any at all.

Two specimens of Augitite (Nos. 64613–4) in the British Museum (Natural History) were collected during the voyage of H.M.S.Challenger (1872–6) and acquired by the Museum in February, 1890, through the Director of the Challenger Office, Dr. (later Sir John) Murray. The rock was briefly described by Renard,1 who noted the fibrous texture and unusual elongation of its pyroxene, as “related to the pyroxenites”.