Pelagic Foraminifera found in the marginal parts of the limestone at Mount Madai in south-eastern North Borneo indicate that it is of Upper Cretaceous age. Much of the limestone at Mount Madai and Mount Baturong does, however, contain algae and other microfossils characteristic of Lower Cretaceous rocks in other parts of the world.

The limestone is provisionally classified as the Madai–Baturong Limestone Member of the Chert-Spilite Formation. Revision of the stratigraphy has clarified the regional structure, and it is postulated that the Chert-Spilite Formation has been uplifted against Neogene sediments along a major zone of thrust faulting.

Consideration of the relative rates of uplift-erosion and erosion-denudation leads to the recognition of nine cases which define the conditions of geomorphological evolution. It is concluded that a peneplanated surface may develop during active tectonic uplift, and that the total volume of clastic sediments produced during any stage is inversely proportional to the rate of uplift.

M'Coy's type material of Hemitrypa hibernica is re-described. The relation between the main fenestelloid structure and the hexagon-mesh superstructure, and the function of the latter, are discussed.

Several species of the Holothurian genus Achistrum, including three new form species, are described from the Ampthill clay of Melton, Yorkshire.

The coiling of the Liassic oyster Gryphaea is discussed and the assessment of tightness of coiling investigated. Hence Hallam's (1960a, b) statistical work on Gryphaea is interpreted and from his original measurements a highly significant increase in thetightness of coiling is demonstrated in the Gryphaeas of the higher Sinemurian horizons of Britain. The presence of a strong natural selection pressure favourable to more tightly coiled individuals of the communities is indicated, and the nature of the lineage discussed. It is suggested that recent criticisms of Trueman's work lack foundation.

Pedicellariae, sphaeridia, and radioles associated with a specimen of Holectypus depressus (Leske) from the Bathonian of Wiltshire, are described and figured.

A simple graphical method is presented for determining the tectonic strain ellipse of a bedding plane from the distorted shapes of randomly orientated brachiopod shells.

Following a bricf survey of previous literature concerning microfossils of the genera Tasmanites Newton 1875 and Leiosphaeridia Eisenack 1958 (generally known as leiospheres), two present day green algae are described (Pachysphaera pelagica Ostenfeld 1899 and Halosphaera minor Ostenfeld 1899). These organisms are compared with members of the fossil genera reviewed above and on the basis of this comparison it is concluded that the biological affinities of Tasmanites and some species of Leiosphaeridia lie with the Chlorophyceae. A possible mode of life is suggested for the fossils and the systematic position of the genera Tasmanites and Leiosphaeridia is reviewed but not altered.

Analyses of eighteen samples from Jurassic marls and limestones show a large, continuous range in carbonate-clay composition. The significance of the carbonate/clay ratio is discussed, and it is show that rapid lateral and vertical transitions from marl to limestone may either reflect major changes in composition or represent only small shifts (across a critical value: 4) in the carbonate/clay ratio. The term “marl” is defined.

The paper discusses the buried channel of the Bristol River Avon. Borehole information indicates a buried channel to a depth of at least — 65 feet O.D. in the Avonmouth area. This has been correlated with other areas and suggests an erosional date of the First or Second Buried Channel Period of the Last Glaciation.