During the course of several journeys from the port of Zeilah southwards across the Ban or Plain to Buramo on the Abyssinian frontier, collections were made of characteristic crystalline rock groups in the hope of elucidating to some degree the composition and early history of the district. Permission to publish these notes was kindly given by the Colonial Office.

“Geologists should think to scale”; so Professor Daly has urged in one of his illuminating writings. Returning from a visit to the Rift Valley country, I realize that in the past I have failed to picture these remarkable valleys to scale. Perhaps I received a wrong impression in the beginning from the rather extravagant language used by some of the earlier writers: “a yawning abyss,” says one; “walls as steep and abrupt as those of a grave,” says another; “in many parts the walls are so precipitous that not even the most expert of cragsmen could scale them,” says a third. Then the well-known drawings of the arch and the sunken keystone, and the rival diagram of the great ramps with a depressed block between them—although I knew that these were only diagrams, not scale drawings, I fear they played their part in perpetuating the early, extravagant impression. So it came to pass that when I stood at last between the walls of the great depression, the glow of satisfaction brought on by the realization of a long-cherished wish was chilled by a rather childish disappointment. Mine was not the case of the man who was shown a giraffe and said “I don't believe it!;”; I believed in the giraffe, but it didn't come up to expectation!

THE fossil material collected from the Ordovician limestones of Akpatok Island, N.W.T., by Mr. Ian Cox during the Oxford Hudson Straits Expedition in 1931, included a specimen whose affinities could not be determined from a superficial examination. In asking me to report on the Polyzoa from these rocks, Mr. Cox suggested that I might also investigate this doubtful form, since it resembled in many respects certain massive Polyzoa. Critical examination by means of thin sections has shown, however, that it is not a Polyzoan but a Tabulate Coral referable to the genus Chaetetes.

1. The anatomy of Helodus simplex Ag. is described.

2. The skull is found to be holostylic, and to have many characters in common with the skull of the Holocephali, but in some respects is less specialized.

3. The pectoral fins, with their long metapterygium, small propterygium, and fused anterior radials, resemble very closely those of the Holocephali.

4. The pelvic and unpaired fins, and general body shape are found to resemble those of the Holocephali.

5. It is concluded that the Cochliodonts are almost certainly closely related to the ancestors of the Holocephali, and the relatively unspecialized condition of the teeth gives support to the view that the holostylic condition of the jaws is primitive for the group. It is suggested that all the Bradyodonts were holostylic, that the hyomandibular may never have been suspensory, and that they may have diverged from the true Selachii before the hyomandibular played a part in the jaw suspension. The difficulties which this view involves are appreciated.

6. The condition of the ethmoid region of Helodus supports the view of the nature of the ethmoidal canal put forward by De Beer and Moy-Thomas (1935) rather than that of Allis (1917, 1926, 1934).

A NUMBER of soil samples were collected from Kalgoorlie, Southern Cross, and other areas in the gold-bearing belt of Western Australia with a view to establishing the relationship between the “ heavy ” minerals of the soils and those of the parental material.

For our present purpose the Craignish Area is considered to include the peninsula of Craignish and its adjoining parts, as shown in the sketch-map, Text-fig. 1.

THE genus Dimorphograptus was founded by Lapworth (1876) for uni-biserial graptolites transitional between Diplograptus and Monograptus, evolution along what is now termed the “ Monograptid trend ” leading to the production of a uniserial proximal portion of the rhabdosome. Akidograptus has been proposed more recently by K. A. Davies for an early stage in the Dimorphograptus series, represented by the species Ak. acuminatus (Nicholson) and Ak. ascensus Davies.

The term “charnockite series” is now commonly in use for a group of genetically related rocks ranging from ultrabasic to acid members having the chemical and mineralogical features of the rock suite of the type area of Madras (Holland, 1893, 1900). The acid member “charnockite” is defined by Holland (1926) as “essentially a hypersthene granite…composed of hypersthene, microcline, quartz, and iron ores…”.

A pegmatite cutting granodiorite contains abundant xenoliths which are in various stages of assimilation. Assimilation involved the conversion by the process of “reciprocal reaction” of the minerals of the xenoliths into species which were in equilibrium under the prevailing magmatic conditions, and the subsequent “mechanical disintegration” of the xenoliths with the strewing of their minerals in the pegmatite. Solution of xenolithic material was not important, probably only affecting potash-felspar. The fact that the active magma was a pegmatite suggests that high temperatures were not available, and its assimilating power must be attributed to its large volatile content. The xenoliths were probably derived from the walls of the pegmatite vein both in the granodiorite and in the country-rocks.

Among other parallels to the structures which he regarded as “crush-conglomerates” in the Manx slates, G. W. Lamplugh (1895, 586–7) mentions beds with isolated fragments in the Bray Series, at Howth, Co. Dublin. The age of this Series of slates and quartzites is rather conjectural. Fossil evidence, founded on such forms as Oldhamia, though supplemented by W. J. Kyan and T. Hallissy, who suggest Middle Cambrian (1912, 249), is inconclusive. More recently, E. Greenly proposes a pre-Cambrian age (1919, 896). The alternating (or greywacke) type of sedimentation seen in the beds recurs many times during Dalradian, Cambrian, Ordovician, and Silurian. Two schools in the interpretation of the Series have to be considered. The older school, with J. Kelly (1853, 240, 253–262) and G. H. Kinahan (1878, 12, 14) as its adherents, ascribed the fragmentation in the shaly beds to volcanic agencies, and, since they failed to distinguish cleavage from bedding, regarded many of the quartzites as intrusive. The younger school, including A. McHenry and W. W. Watts (1898, 17) and Lamplugh (1903, 6), described the breccias as produced by friction during regional earth-movements. The latter, as W. J. Sollas puts it (1893, 98), possibly extended from post-Ordovician to post-Carboniferous. While the effect of later crushing and faulting must not be overlooked, it seems necessary i n the light of recent work by E. B. Bailey (1930, 86–90), Bailey and J. Weir (1932, 429–458), and S. M. K. Henderson (1935, 487–509), t o invoke probable seismicity and contemporaneous slumping to explain the alternating beds and associated shaly breccia. A new suggestion will be advanced regarding the quartzites.

Following the recent discovery at Sandling (near Hythe) of a Hypacanthoplites of the group of H. milletianus (d'Orb.) in place (i.e. below the regularis level), and still comparatively high up in the Folkestone Sands, collecting at this locality was intensified, for it was realized that we now had the attractive possibility of bridging over for the first time the enormous time interval separating the latest Aptian faunas from the earliest known Albian examples of this country. Unfortunately in this respect we were to be disappointed, for although further ammonoid faunas were brought to light, they proved to be of uppermost Aptian age, and therefore substantiated this gap in the British sequence. However, despite that we have been able to extend the Aptian high into the Folkestone Sands, what is more important, we have obtained the first indication of a milletianus fauna in this country.

In 1933 the present writer described and mapped an igneous complex in the counties of Tyrone and Derry in Northern Ireland, to which he gave the name of the Tyrone Igneous Series.

Last summer Miss D. L. Reynolds kindly organized an excursion of ten, all told, to discuss her recent paper on “The Eastern End of the Newry Igneous Complex”(Quart. Journ. Geol. Soc., xc, 1934, p. 585). We were introduced in most helpful fashion to both field exposures and microscope slices. In some particulars, differences of interpretation arose; and at the conclusion I circulated a brief memorandum. This by request I now offer, with trifling changes, for publication. Page and figure references, unless otherwise defined, apply to Miss Reynolds's paper.

Prior to a discovery made recently by the writer, of spilitic rocks at Great King Island, the largest member of the Three Kings group of islands, about 26 miles north-west of the north-west extremity of the mainland of New Zealand, such rocks had not previously been found in this latter country. Some account of the types represented at Great King Island may therefore be welcome, particularly since Gilluly's (1935) recent comprehensive paper has focused attention on spilites and their associations.

The nodules examined have been shown to contain a variety of minerals and to exhibit certain mineralogical and structural differences from one another or within the nodules themselves. The mineralogical differences serve to separate five definite types of mineral facies. There are also described types transitional between the nodules themselves, and between them and the surrounding rock, grading from types sufficiently aluminous to exclude the formation of wollastonite to less aluminous types in which this mineral is formed.

Owing to insufficiently prolonged variations of the metamorphic conditions equilibrium has not been established, and a remarkable series of replacement structures has been left in the rock by means of which the course of several stages of its metamorphism has been established.

Lack of knowledge concerning the metamorphic conditions previous to changes due to the influence of the surrounding diorite, the isolated character of the nodules and the intricacy of the relationships between the minerals render the origin and metamorphism of these nodules subject to a variety of interpretations. The balance of evidence seems in favour of the one put forward here.

Both geologists and archaeologists will be under a debt of BOTH gratitude to Messrs. King and Oakley for their recent paper on the Pleistocene sequence of the lower part of the Thames Valley (I). Not only have they conveniently summarized the results obtained by other field-workers, but they have contributed two postulates of great importance. These are: (a) the probability of a major period of erosion between the deposition of the Lower Loam and the Middle Gravel of the Boyn Hill Terrace succession; and (6) the recognition of a period of erosion between the formation of the Lower Flood Plain Gravel and the Post-Pleistocene alluvial beds.

WHILST working through a batch of slides of heavy minerals of the Millstone Grit of the Pennine region some interesting outgrowths on zircon have been noticed which are worthy of record. The writer is not aware that they have been recorded before, but they must have a wider distribution than the Millstone Grit of this area, and therefore this mention of them may lead to further records being made known.