In a letter published in the March–April, 1942, number of this magazine I said I hoped to continue working on the problematical bodies found in rhyolite-ash in Malaya and first described by me in 1930. Further work has been done, but before giving the results I must mention the unusual sequence of events that has led up to the present paper. My identification of “rods, spheres, and club-shaped objects” as spongeremains in 1930 (the work was chiefly done in 1928) was then supported by Dr. M. Burton, who thought they came from marine sponges; but in February, 1942, he withdrew this support. In Annual Reports for 1937–1940 Mr. E. S. Willbourn, Director of the Geological Survey, Federated Malay States, recorded more outcrops of this ash and mentioned the discovery by Mr. H. D. Collings of stone axes in gravel of probably Mid-Pleistocene age below the ash. Supported by Dr. K. P. Oakley, Mr. H. D. Willbourn queried the problematical bodies being sponge-spicules.

In a recent study of the growth stages of Promicroceras marstonense (Currie, 1942), it was shown that apart from slight individual variations, the growth-ratios exhibited changes at certain stages, which are characteristic of the species. A similar investigation has now been carried out with material representing other species of Promicroceras, in order to ascertain how far there is general agreement within the genus and the extent to which any differences are typical of the various species studied.

Zaphrentoid faunas occur in the Middle and Upper Viséan of Great Britain, but have not been adequately described and so are difficult to distinguish. Probably the most fossiliferous of such Upper Viséan faunas are those found in the D2–3 shales and grey limestones with chert which occur near the top of the Lower Carboniferous beds of Derbyshire. A characteristic form in these faunas is that usually assigned to Zaphrentis costata (McCoy), a species imperfectly known and inadequately described. In 1937 I collected such forms from Cawdor Quarry, Matlock Bridge, Derbyshire, with the intention of identifying and redescribing the species. Since then sections have been made from the lectotype: these sections, however, are imperfect and a specific description based on them by Hill (1940, p. 137) is necessarily incomplete. The specimens from Cawdor include one which is similar to Z. costata but which shows successive contractions of the corallum and a change from straight to waved and corrugated major septa, a phenomenon possibly due to “gerontism”.

Among the most notable features of the geology of Yorkshire are two parallel structures known as the Cleveland and Market Weighton anticlines. Although they are parallel and not far distant, it has often been pointed out, and especially by Kendall and Lamplugh that these structures differ in almost every possible way. The Market Weighton axis has now no topographical expression at the surface, whereas the Cleveland axis forms the watershed of one of the most clearly developed river-systems of the country. The first and most obvious meaning of this is that the Cleveland axis moved during the Tertiary, while the Market Weighton axis did not. But the real fundamental difference goes much further back than that.