Although Thomacystis is clearly a hemicosmitid cystoid, it cannot be included within existing families, and the new family Thomacystidae is therefore proposed to accommodate it.

The rocks of the Skiddaw Group of the Black Combe inlier were subjected to low grade regional metamorphism during the D1 movementphase of an intra-Lower Ordovician orogenic episode. Mimetic recrystallisation of clay minerals parallel to the bedding was ubiquitous. Later, axial-plane cleavages were superimposed on this fabric. The nature of the cleavages and possible mechanism of their formation is discussed.

Silica has been mobilised on at least three occasions during the tectonic history of the inlier. In no case was this due to metasomatism but simply to metamorphic differentiation. The D1 veins are of either quartz, or quartz and chlorite whereas veins of later generations are of quartz alone.

The field of composition and the geochemical trend of the lower portion of the stratiform Stillwater igneous complex correlate well with the field and trend for alpine-type ultrabasic masses in the nearby gneissic basement of the Beartooth Mountains. This is consistent with a derivation of some alpine-type masses by the tectonic disruption and metamorphism of stratiform complexes.

Eight species of foraminifera from the Manchester Marl are described and foraminifera recently discovered in the Magnesian Limestone of both the West Cumberland and the Eden Valley areas are also mentioned. All the described forms are similar to, and some are possibly conspecific with, foraminifera previously recorded from the Lower Magnesian Limestone of north-eastern England or Zechstein 1 of north-western Germany.

A metamorphosed complex of basic and acid gneisses, which occurs in north-west County Mayo, Ireland, structurally underlies younger Moinian and Dalradian type metasediments. These gneisses are compared directly with the Lewisian ‘inliers’ of the western Highlands of Scotland.

Core material from carbonate cemented sandstones of Eocene age from the Maracaibo Basin, Venezuela, exhibits evidence of post-burial sideritisation of calcite. the process being identical in its essentials with dolomitisation. and resulting in a marked increase in porosity and permeability of the cemented sandstones. As a result of this increase, sub-surface waters have been able to leach out much of the sideritc cement, and subsequent mechanical compaction of the sandstones has produced a characteristic “bead”-like arrangement of remnant sideritc granules around the sand grains. The whole process can be reconstructed from thin-sections, and these are used to illustrate the text.