In the schistose grits of the Dalradian Series north of Stonehaven there is clear evidence of the deformation of the rock by shearing of the original quartz grains along planes roughly diagonal to the “flattening”, which here coincides generally with the schistosity of the quartz-schist, the final product of the metamorphism. As this corresponds essentially to the case studied by Schmidt and others, an examination of the rock fabric is made having in mind the mechanism suggested by Schmidt, and more fully elaborated by Anderson, to connect up crystal orientation with deformation. The results of the study do not indicate that the simple model of equal spheres, each with its set of glide planes, and all in cubical packing, is in any way adequate to explain the petrography of this quartz-schist and it is suggested that any theory that makes a purely mechanical reaction of the quartz grains to the deforming forces the dominant factor in the production of a new texture is at variance with the facts since there is clear evidence of the continued solution and crystallization of quartz throughout the whole of the metamorphic period.

A plea is made for the wider use of concise descriptive phrases instead of rock-names of the conventional type, which are usually uninformative. The writer's case is discussed in relation to the so-called “mugearites”.

Ten clinopyroxenes have been investigated chemically and optically. Eight of these were separated from the rocks of the Garbh Eilean sill and two from other rocks relevant to this inquiry into the trend during crystallization of pyroxenes in minor basic intrusions of mildly alkaline and undersaturated type.

The marine Johnstone Shell Bed, an important index horizon in the Limestone Coal Group of the Carboniferous of Scotland, is succeeded in North Ayrshire by a bed containing Lingula squamiformis Phillips, and many small shells here referred to a new species of the genus Carbonicola. This Carbonicola community has been examined in detail, and graphical representation of the great variability has been employed.

Previous descriptions of the plastron of Somaliaster Hawkins have been conflicting and, in consequence, there has been some doubt regarding the systematic position of this genus. The type-material has been re-examined and the plastron found to be meridosternous. Somaliaster is here referred to the family Stenonasteridae, where it has close affinities with Iraniaster Cotteau and Gauthier.

The paper records the results of petrofabric analyses of four specimens of marble from the South-West Highlands of Scotland. The marble fabric has a high degree of homogeneity. Calcite grains are flattened in the foliation plane and are elongate in a direction normal to the fold axis. The c crystal axes lie in a distinct girdle about b, with a maximum near the pole of the foliation; the a crystal axes tend to occupy three maxima, one of which is close to b. Late twinning has occurred on {011¯12} apparently in response to a simple stress system, operating in the ac plane. The symmetry of the general calcite fabric, the twinning and the megascopic structures coincide.

The inversion temperatures of the quartz from twenty-five specimens of the Beinn an Dubhaich granite have been measured and found to correspond to the inversion temperatures of quartz from rhyolites previously studied. Optical and X-ray studies of the alkali and plagioclase feldspars indicate high temperature modifications. The Beinn an Dubhaich granite has the textural and compositional features of a granite together with mineralogical features normally associated with rhyolitic rocks. The results serve to emphasize that methods are now available which make it possible in some cases to determine whether a particular granite was formed by metamorphism of sediments or by crystallization of a magma. It is concluded that the older granites and those which crystallized at greater depths probably have undergone considerable rearrangement of their mineralogical and textural features subsequent to primary crystallization.

Evidence strongly suggests that the Durness Limestone in Skye is a great thrust-slice between Torridonian above, at Broadford, and Torridonian below, at Strollamus and Scalpay.

In a Tertiary ring complex at Carlingford, Eire, a large mass of eucrite is cut by porphyritic cone-sheets. A major granophyre intrusion later than the cone-sheets alters the clinopyroxene of the sheets to hornblende whilst the clinopyroxene of the adjacent eucrite remains unaltered. By elimination of several possibilities it is shown that the different behaviour of the two pyroxenes reflects their thermal stabilities.

It is argued that the two pyroxenes represent a pyroxene trend of crystallization and that thermal metamorphism attacked them in the reverse order of their magmatic crystallization. Importance is attached to extensive replacement of Ca′ by Fe′ in the cone-sheet pyroxene as a factor of instability.