The area containing the quarries discussed in this paper extends inland from the City of Aberdeen for a distance of about twenty miles and is bounded on the north and south by the rivers Don and Dee. This is the area of the Newer Granites of Aberdeenshire, which C. B. Bisset has described in “A Contribution to the Study of Some Granites near Aberdeen” and has divided the acid igneous rocks into:—

1. The Skene Complex: consisting of diorite, adamellite, grey granites, transition types and minor intrusions.

2. Later Group: consisting of coarse red granites.

Some years ago (Phillips, 1937) I published the results of a preliminary survey of the fabric of some Moine schists by the methods which have been evolved in that branch of the study of rocks now generally known as structural petrology. This survey showed that the quartz, muscovite, and biotite in all the specimens of Moine schist examined have the girdle-arrangement characteristic of a B-tectonic; that the b−axes of these girdles, over a large area of outcrop, plunge in a south-easterly direction; and that the direction of the b−axis of a given specimen is frequently marked by a visible lineation on the foliation-surface of the schist. Study of the fabric of Moine schists visibly affected by the dislocation-phase of the post-Cambrian movements was shown to afford support for the view, already advanced by others on the basis of petrographic study, that the ultimate effect of these movements on the Moine schists is to break down the previously existing fabric; there is a dislocation-metamorphism “undoubtedly superposed upon the general Moine metamorphism” (Read, 1934, p. 307).

In the course of discussions on Echinoderms between the senior and junior authors, the family Cromyocrinidae came under scrutiny and in view of a vital link of evidence in the form of a Pennsylvanian (Upper Carboniferous) specimen of Ulocrinus buttsi Miller and Gurley with the arms attached, found by the junior author a few years ago, the following interpretation of the family is suggested.

In a recent description of a composite teschenite-picrite sill at Saltcoats in Ayrshire (Patterson, 1945), mention was made of a potash-rich variety of lugarite which occurs as a differentiate of biotite-teschenite. The latter rock was emplaced at an intermediate stage in the intrusion cycle of the sill, being preceded by a flow-banded teschenite and followed by hornblende-picrite. Differentiation of the biotite-teschenite took place in situ and had proceeded to a considerable extent before the picrite was intruded along the middle portion of the former rock, splitting it into an upper and a lower layer. Richness in volatile constituents was a characteristic of the biotite-teschenite magma and facilitated the process of differentiation (Tomkeieff, 1937, p. 85; Smyth, 1913, p. 33). The separation of an alkali-rich fraction which resulted, is seen in the field by the appearance of pink analcitic patches or “blebs” in the teschenite at a distance of a foot or so from the margins. Further from the contacts, where cooling conditions were more gradual, these analcitic areas increase in size and frequently coalesce to form veins, which themselves intrude adjacent areas of biotite-teschenite. The veins are pink in colour, and contain varying amounts of conspicuous acicular crystals of barkevikite and titanaugite. Petrologically they are similar to the lugarites of the Scottish Permo-Carboniferous suite (Tyrrell, 1917). In chemical composition they also resemble the type lugarite, with the important exception that the Saltcoats rock is much richer in potash, although the sum of potash and soda is little different. A close analogy is provided by covite, from Magnet Cove in Arkansas (Washington, 1901). On account of the close relationship of the Saltcoats rock to the Scottish teschenites, it was preferred to name the rock potash-lugarite.