This paper describes the development from the initial prosicula of the rhabdosome of Diplograptus cf. (Amplexograptus) maxwelli Decker. Points of comparison with other diplograptid astogenies are noted. Evidence about the structure of the interthecal septum is brought forward and so stages in the formation of one thecal segment can be defined. Mention is made of some abnormal specimens.

Of the three main lithological units on Cuilcagh, namely, Millstone Grit, Yoredale Sandstone, and Yoredale Shale, particular attention is paid to the latter which attains a thickness of 700 feet. Numerous goniatites were collected from the lowermost 450 feet of it and these establish the existence of the P1b, P1c, P2, E1a zones and possibly the E1c zone also. Higher beds are very poorly fossiliferous and their age is uncertain. Brief comparisons are also made with Yoredale Beds in England and in other parts of Ireland.

The diorites and Sron a' Chro' granite of the Glen Tilt complex enclose hornblende-schist xenoliths derived from the Dalradian epidiorites of the country rock. Small hornblendite xeoliths are found in the complex but are restricted to the diorite outcrop. Porphyroblastic hornblende is developed within the schist xenoliths and reaction zones rich in hornblende are formed around the xenoliths. The mineralogical and textural characteristics of these reaction products suggest that the typical two-hornblende generation appinites of the complex represent modified hornblende schist. A similar origin for the quartz-orthoclase-appinite of the complex is rejected and their development from hornblendite is indicated.

Well-defined genera of ammonites from the Toarcian, Bathonian, Oxfordian, Kimeridgian, and Tithonian are diagnosed and named.

It is generally accepted that the continents contain more radio-activity than the Pacific floor. The two continents, Laurasia and Gondwanaland, would therefore expand the rocks below, relative to that floor. The plastic substratum under the continents would be forced higher in their centres than at their centres than at their Pacific margins. It would creep towards those margins and would carry part of the overlying granite to them, piling it high at their margins and thinning it at their centres. The plastic substratum would continually carry its heat to the cold Pacific substratum and render it plastic into which the continents would be impelled.

After establishing average velocity of wind/average porosity curve for wind deposited sands, where it was shown that low wind velocity produces higher porosity than high wind velocity, further investigation was made and sands of various characteristics were used. It was established that the velocity of wind/porosity of deposit relationship is a more complicated function than was previously expected and some of the reasons are explained. The first indication of the influence of shape of the grain and the specific gravity of grains on the obtained results is registered. Further steps in the research are indicated.

In the search for large deposits of haematite and other feebly magnetic minerals, it is suggested that mapping the magnetic residuals may be of greater value than mere linear traverses. Not only is the method more suitable for exploring virgin areas, but it also affords a means of differentiating between the effects of large deeply buried masses and small objects at shallow depths. At the same time, the graphical expression of the results on the map becomes more easily intelligible.

The application of the method to known haematite ore-bodies in South Wales has yielded striking results and the extension of the survey into an unexplored area indicates the possibility of proving at least one further large haematite deposit.

A new species of Palaeechinus, and the first certain member of that genus from North America, is described and several unusual features of its test noted. The apical disc of the specimen is extremely well preserved.