Societies and Academies

Abstract

LONDON. Geological Society, March n.—O. T. Jones: The geology of the Llandovery district (Carmarthenshire). The district lies east of the town of Llandovery, and extends for about 10 miles from north-east to southwest. It is divisible into a northern area and a southern area, each area the succession is fairly complete, but in between them it is greatly attenuated. In proceeding from south to north, certain lithological changes have been noted in the Lower Llandovery. The fauna in the rocks appears in the main to have been drifted into the area from an adjoining tract, lying probably nearer to the shore-line. In addition to the differential subsidence and uplift along lines trending north-east and south-west, there is evidence of repeated elevation and depression along nearly east-and-west axes. The axes of these transverse movements appear to have persisted during the whole of the Llandovery epoch, but there is no evidence of them in the Wenlock rocks.--G. Andrew: (i) The Llandovery and associated rocks of Garth (Brecon-shire). The Llandovery rocks lie north-west of Garth railway station, and extend from there in the direction of Newbridge. The Lower Llandovery rocks overlie the Bala with a sharp boundary, but with apparent conformity. The Middle Llandovery occurs in one small outcrop in the centre of the area, and is rapidly overstepped by the Upper"Llandovery in both directions. The Upper Llandovery consists of two types, a lower comprising sandy mudstones with Pentamerus oblongus, etc., and an upper of pale mudstones ("Tarannon Pale Shales "). (2) The relations between the Llandovery rocks of Llandovery and those of Garth. At Garth, as at Llandovery, the Lower and Middle Llandovery rocks are overstepped both north and south by Upper Llandovery or Wenlock deposits. At Garth they crop out Jin an elongated oval area; at Llandovery they form two roughly oval areas. The Middle Llandovery and the higher divisions of the Lower Llandovery are represented only in the central regions. These distributions are due to the fact that differential movements along nearly east-and-west axes (that is, transversely to the present strike) were in progress during the Llandovery epoch. The regions where the older Llandovery rocks are most complete were regions of persistent subsidence. The axes of elevation in both areas cross the present strike at practically regular intervals of about 5 miles, and the areas of subsidence are situated nearly midway between them. Linnean Society, March 19.—S. Hirst: Species of mites of the family Trombidiidae found on lizards. When more than one form occurs on the same host, a flattened form lives under the scales, and a rounded form between the toes or toe pads. In view of the considerable differences in the shape of the setae, etc., these are regarded at present as distinct species.-o Mrs. Muriel Roach: A study of the physiology of certain soil alga; in pure culture. Although a very few species carried on the synthesis of organic substance from carbon-dioxide and water through the agency of sunlight, the great majority of those studied grew much better when supplied with an additional source of carbon, glucose being especially favourable to many species. A single species was selected for a more detailed investigation of the effect of different organic substances on its growth in liquid media. The alga was able to grow in complete darkness, given a suitable supply of food, at about half the rate that it grew in the same medium in the light. The logarithmic values of the bulk for the first nine or ten days, in media completely favourable to the growth of the organism, lie on a straight line. The data indicate the importance of the compound interest law which evidently underlies the growth of the organism during the initial part of its growth. The theory of the auto-catalytic nature of growth does not appear to hold.-J. M. Brown: Some Collembola from Mesopotamia. Fifteen species of Collembola collected mainly in the neighbourhood of Bagdad and Amara, in Mesopotamia. Ten species and one variety are regarded as new. The Collembolan fauna of Mesopotamia shows much closer affinity with that of the Palasarctic than with that of either the Oriental or the Ethiopian regions.