Northern Iceland between Skagafjord on the west and Skjalfandi Bay on the east is a deeply dissected upland built up of plateau basalts with subordinate intercalations of clastic volcanic sediments. The main valley, the Eyjafjord, is traceable northwards as a groove in the sea floor down to–500 metres. To the east of the upland the country is less elevated; marine Pliocene deposits are present in the Tjörnes peninsula, and recent lava flows are prominent. The contrasted regions adjoin along the BarQardal fault running N.–S. and marking the western boundary of the great graben which has been the site of Recent and Quaternary volcanic activity. Thoroddsen considered the upland rocks to be Tertiary (Miocene) in age, and that the Pliocene sediments had been laid down in a bay formed after the faulting and erosion of the older series.

The occurrence of andalusite and sillimanite in unaltered igneous rocks is, according to the orthodox view expressed in most standard textbooks (see, e.g., Tyrrell, 1934, pp. 50, 164; Shand, 1927, pp. 62, 146; Grout, 1932, p. 230), always to be ascribed to contamination of magmas by highly aluminous sedimentary or metamorphic rocks. Having been given cause to doubt the correctness of this view by the recognition at Pyramid Hill, Victoria, of andalusite-bearing granites and aplites in which evidence of assimilation is lacking, I was then very interested to discover that the opinion has often been expressed, and evidence adduced in support of it, that both andalusite and sillimanite may be normal pyrogenetic constituents of igneous rocks.1 That is, they may under certain conditions crystallize from uncontaminated magmas. Some authors, while admitting that andalusite and sillimanite may crystallize from magmas, regard such pyrogenetic occurrences of these minerals as caused by the development of local excess of alumina, due to the assimilation of shales (e.g. Wells, 1931; Shand, 1927, p. 62). Others do not make their position clear, merely classing andalusite and sillimanite as assimilation minerals (sic), but Tyrrell goes so far as to state that they are “never of pyrogenetic oiigin” (1934, p. 50). Because of the reliance that is placed upon accessory minerals in igneous rocks as indicators of consanguinity of magmas and of the role of assimilation and other processes in pedogenesis, it is important that the status of each mineral should be thoroughly understood. In most classifications of accessory minerals andalusite and sillimanite are either classed as “contamination accessories” (Wells, 1931) or grouped with minerals that are commonly due to contamination (Wright, 1932), and Wright regards them as “of little value for correlation purposes”. Chatterjee, however, was able to use andalusite as an indicator, on the one hand, of relationship between the Falmouth and Bodmin Moor granites, both of these containing a purple variety in fair amount, and, on the other, of the distinction of these granites from those of Dartmoor and St. Austell, in which andalusite is colourless and rare. The rare, sporadically developed andalusite in the Dartmoor granite is considered by Brammall and Harwood (1923) to be a contamination mineral, but Teall suggested (1887) that the andalusite in the Cheesewring granite is probably an “original constituent” (i.e. not mechanically incorporated with the granite, as strew from xenoliths or wall rocks), and the relative abundance and uniformity of distribution of andalusite in the normal type of the Bodmin Moor granite, as exhibited at the Cheesewring (see Ghosh, 1927), lend support to this suggestion.

Before I went to Malaya in 1903 I had worked for two field seasons in Cornwall as a very junior member of the staff of the Geological Survey, and since my retirement in 1931 the old interests in Cornwall have attracted me, with the result that from 1935 onwards I have been doing field-work each year in the Lizard Peninsula. My original object in going to this part of Cornwall, armed with the 1912 Geological Survey Memoir (The Geology of the Lizard and Meneage, J. S. Flett and J. B. Hill) and the two 1-in. maps dated 1912 and 1934, was humbly to follow the work of my seniors in a part of Cornwall to which I had not previously penetrated, without any idea of criticism; but, although anyone who is conversant with the geology of the Lizard must agree with by far the greater part of the 1912 Memoir, in the course of my very enjoyable trips, during which I had the advantage of discussions with Sir John Flett and Dr. E. M. L. Hendriks, points have cropped up that are new or present problems on which I cannot see eye to eye with the surviving author of the Memoir, who has suggested that I should publish my results before he produces a new edition.

The following faunal list provides a comparative summary of the Palaeoniscids of the chief Border Cementstone localities:—

Foulden.

Styracopterus ottadinicus (White).

Carboveles ovensi White

Aetheretmon valentiacum White

Aetheretmon valentiacum var. ovensi White.

Aetheretmon whitei sp. nov.

Strepheoschema fouldenensis White.