In the west of the Isle of Rhum (Inverness-shire), Tertiary acid rocks outcrop over an area of approximately 6 square miles. A core of spherulitic microgranite is surrounded by graphpphyre1 which, in turn, is bounded on the north by Torridonian Sandstone; although much of the boundary is marked by a low-angle reverse fault, part of the junction is undisturbed and a belt of transitional rocks, some 1,400 feet in width, intervenes between the graphophyre and the Torridonian Sandstone. The transitional rocks are divisible into five zones which are interpreted as marking successive stages in the conversion of sandstone into graphophyre. Evidence is presented indicating that the microgranite, into which the graphophyre grades inwards, represents a still more advanced stage of transformation.

The pegmatites of Trolvis Quarry, Carnmenellis, are small lenticular masses which were developed before the joints of the associated granite. Both mineralogically simple and complex types occur: the latter are drusy. Whilst the earlier minerals lining the druses may have crystallized in a closed system, the later minerals were clearly deposited from a moving phase. The disposition of the later minerals was largely determined by earlier crystals acting as baffles to the mineral-depositing agents. The pegmatites appear to occupy spaces formed by the solution of the granite by a pegmatitic fraction of the magma.

A complex of granitic, syenitic, and dioritic rocks forms the western part of the Insch mass. All these rocks appear to be related, but they are later than, and have no direct connection with, the basic rocks forming the bulk of the Insch mass. The granitic and syenitic varieties are fairly uniform, but the dioritic types are variable rocks rich in xenoliths which are apparently derived from basic rocks. It is suggested that the diorites were formed by contamination of the magma producing the granitic and syenitic rocks.

The Quartz-dolerite intrusion of Sgùrr nam Meann, Ardnamurchan, is shown to be a ring-dyke which has sill apophyses extending from its outer wall. This is a form of intrusion which has not been recognized before, and its field relations are described in detail. The quartz-dolerite is extensively veined by acid rocks which are ubiquitous in all parts of the intrusion, and most abundant in the sills. From the evidence of the distribution and nature of the veining it is concluded that the acid and basic components of the intrusion must have been ernplaced simultaneously. It is suggested that a gas-charged, acid residual magma may have separated from a crystallizing basic parent under the influence of sudden reductions of external pressure acting upon the system.

The brickearth of Pegwell Bay in Kent is identified as a true loess. It rests on solifluction deposits and frost-shattered rocks.

The hypostome of a specimen of Encrinurus variolaris (Brongniart) from the Wenlock Limestone (Silurian) is described with particular reference to the intricate shape of the lateral wing. This lies very closely underneath the axial furrow of the cephalon in the region of the anterior pit, but it is unlikely that there was a direct articulation of the wing with the pit or the furrow during life.

Cyrtograptus hamatus, first described from Ireland by Baily in 1862, is now described more fully from fresh material which can be assigned to the zone of C. lundgreni. The proximal part of C. lundgreni is also described. Three species of Retiolitids occur with the Cyrtograptids, one of which, Paraplectograptus eiseli Manck, has not previously been recorded in the British Isles.