The latest studies of fossil Mammals appear to show that the Upper Pliocene and Pleistocene mammalian faunas of Europe were chiefly immigrants from the Asiatic region (35). The corresponding faunas of Africa seem to have been derived chiefly from the same source (28, 35). The distribution of the stone implements of Palaeolithic Man also can be best explained by supposing that the successive human races who made them started in Asia, and migrated westwards in two divergent streams to Europe and Africa respectively (6). Until the latest phase of the Pleistocene, there cannot have been any direct communication between the men of northern Africa and those of southern Europe. Man, indeed, like the other mammals seems to have originated in the Asiatic region.

The following descriptions are based on specimens recently collected in the Ordovician rocks of the Girvan area by Mr. James L. Begg and Mr. R. Tripp, and are all new species of interest.

The Upper Palaeozoic rocks at Wickwar pass eastwards below Mesozoic strata, but about half a mile farther to the east the pre-Triassic surface is laid bare in places in the floor of the Little Avon River for a distance of 1,300 yards between Stmt Bridge and a point some 360 yards below Horse Bridge. The rocks found here are of Silurian age. Exposures are small and discontinuous since the stream has covered the valley floor with its own deposits and only at intervals does it flow on, or cut laterally into the solid rock. Moreover, the base of the Trias, which is nowhere many feet above the thalweg, sinks twice below stream level, dividing the Silurian outcrop into three inliers. The first two, conveniently styled the northern and southern Sturt Bridge Inliers, are separated by only 40 yards of Triassic deposits, but between the more northerly of these and the Horse Bridge Inlier 330 yards of Triassic rocks intervene.

The two Palaeozoic ranges, the Caledonian and the Hercynian, were comparable in size with the Alps. In his chapter on the European Altaids, F. E. Suess1 says “Recent investigations have brought evidence that the original Variscan mountain chain of which now only scanty remains are left, was once not inferior in size and extension to the Alps to-day”. The remains of both ranges are now at a low level, and it was for some time tacitly accepted that that low level was due to denudation through the long period since they were formed. That low level is not, however, consistent with isostatic theory. Isostatic theory requires that a mountain must have strong roots immersed in a heavier plastic medium so that in effect the chain and its roots float “hydrostatically” in that medium. Accordingly if a layer h km. thick and density p is removed from the top of the range, the level of the range will fall by h (1 − /σ) where σ is the density of the plastic medium. If p = 2·6 for granite, and σ = 2·85 for the intermediate layer, the level will fall by − km.

The existence of pillow lavas, black shales, and cherts in North Glen Sannox, Arran, has been known since W. Gunn carried out the detailed mapping of this part of the island for the Geological Survey in 1899. A description of these rocks, in which that author makes the suggestion, not since seriously disputed, that they are of probable Arenig age (Gunn, 1900) was first published in the Summary of Progress for 1899. Full accounts, to which the reader is referred for details not repeated in the present paper, were later given by Gunn (1903, 1905) and by Tyrrell (1928).

The limestone xenoliths about to be described were collected on the eastern side of Barnavave from a disused quarry situated at the junction between the “junction hybrids” and the surrounding Carboniferous limestone. The material comes from loose blocks left over during quarrying operations. Both the hybrids and the metamorphosed limestones have been dealt with in detail elsewhere1 and will only be referred to incidentally here.