The following description of new genera and species of Lower Ordovician Cryptolithids is the result of a stratigraphical and palaeontological investigation of the rocks in the Llangadock-Llandeilo district, Carmarthenshire.

Among the most controversial problems of British geology are those concerning the metamorphic rocks which make up the greater part of the Scottish Highlands. The writer, in common with many geologists whose work has brought them into contact with the region, has long felt that the discussion and solution of these problems would be greatly facilitated by a nomenclature less involved and more consistent than that at present in use. A simplified nomenclature, moreover, would do much to stimulate and hold the attention of students and general readers.

Since the publication in 1880 of Nicholson and Etheridge's monograph of the Ordovician and Silurian fossils from Girvan, no further work has been done on the coral faunas of that region. While engaged on a revision of the rugose corals as a whole, I have studied a part of the Gray Collection in the British Museum (Nat. Hist.), of which the present article is an outcome. I am grateful to the keeper of the Department of Geology, and to Dr. H. D. Thomas for the loan of material and for the kind interest shown in my work, and to Dr. Stanley Smith for his valuable criticism and advice. This work was mainly carried out in the Sedgwick Museum, Cambridge, and I take the opportunity to express my thanks to Professor W. B. R. King and Mr. A. G. Brighton for facilities for study. Dr. H. D. Thomas and Dr. O. M. B. Bulman both kindly read the manuscript.

During the war a large new quarry was opened in the Longmyndian rocks of Haughmond Hill, Shropshire. It is near the south-east edge of the hill, to the west of the road running north from Upton Magna and one mile from the village. On the sketch-map in the Shrewsbury Memoir (p. 58) two arrows are shown, at about this locality, recording dips of 50° in a south-easterly direction. I was told that there was a very small quarry here before the large quarry was excavated. The present quarry is even larger than that near Haughmond Abbey (Shrewsbury Memoir, p. 48), on the north-west side of the Pre-Cambrian outcrop, and the two quarries offer extensive and splendidly displayed exposures of Longmyndian rocks, one in the coarse-grained Western Longmyndian and the other in the fine-grained Eastern Longmyndian.

In 1940 Professor O. T. Jones published in the Geological Magazine significant observations on certain of the Lower Palaeozoic contacts in north Pembrokeshire. His detailed inspection of the Solva-Caerfai contact at Caerfai Bay, and the Arenig-Lingula Flag junction at Whitesand Bay, revealed erosional and depositional features which clearly established hitherto debatable lines of unconformity. In addition, his results have aroused much needed assiduity in the interpretation and inspection of formational breaks in the Lower Palaeozoic rocks. Shearing and structural deformities, as well as the emplacement of cleavage, frequently mask such erosional and depositional features but, as Professor Jones has demonstrated, vestiges of them sometimes remain.

The first systematic study of anal variations found among various Carboniferous crinoids was presented by James Wright (Geol. Mag., lxiii, 1926) and covered Eupachycrinus calyx (McCoy) (now Phanocrinus Kirk) and Zeacrinus konincki Bather. Subsequently (Geol. Mag., lxiv, 1927), the genus Hydreionocrinus, and Ulocrinus globitlaris (Geinitz) (now Ureocrinus Wright and Strimple, Geol. Mag., lxxxii, 1945) were also considered. A total of 2,014 dorsal cups from the Scottish Lower Carboniferous (Mississippian) were involved in the examinations. These specimens were all from strata considered equivalent to the Chester Series (upper Mississippian) of North America. When presenting the genus Phanocrinus Kirk (Journ. Paleont., 11, 1937) recognized the importance of Wright's studies, but noted that examination of an almost equal amount of American material (primarily the Springer collection of the U.S. National Museum) had failed to disclose such great variations. That Kirk was highly impressed by Wright's studies is certain, for in personal conversations, several years ago, he emphasized the potentialities as they might affect my impending studies of Pennsylvanian crinoids. It has, therefore, been with much interest that I have watched similar patterns of development appearing in the large collections being made from both Chester (Upper Mississippian = European upper Lower Carboniferous) and Missouri (Middle Pennsylvanian = European middle Upper Carboniferous) of north-eastern Oklahoma.