Reports and Proceedings — Geological Society of London. 47 



The Archgean rocks protrude in a few places through the sedi- 

 mentary beds, which form the greater part of the area, and consist 

 of an igneous complex t)f rocks of varied composition. 



The Cape System is capable of division into five distinct series : — 



Z' Magaliesberg and Gatsrand series; alternating quartzites, shales, and 

 -TT I lava-flows. 16,000 to 20,000 feet. 



Beds^ { Dolomite and cherts, thickly bedded. 6,000 to 8,000 feet. 



' ■ I Black Reef ; a bed of quartzite and conglomerate, 20 to 50 feet, and 

 \ Klipriversberg amygdaloid ; a basic volcanic rock, 5,000 to 6,000 feet. 



iWitwatersrand Beds; sandstones and conglomerate (in part auriferousj. 

 11,000 to 15,000 feet. 

 Hospital Hill series ; quartzites and ferruginous shales. 8,000 to 

 10,000 feet. 



A full description of each of the series, and the associated volcanic 

 and igneous rocks, is given in the paper. 



The Karoo formation is represented by the Coal-measures of 

 Vereeniging and the district south of Heidelberg, and by the 

 measures of other coal-areas. They have furnished plants which 

 Mr. Seward refers to in a note as being of Perrao-Carboniferous age. 



The age of the Cape System is doubtful. The Upper beds rest 

 uncon form ably on the Lower ones, and if the latter be of Devonian 

 age, as has been inferred, the former may represent the Lower 

 Carboniferous rocks. 



In conclusion the author makes some observations upon the 

 geotectonic relations of the area. 



3. " Observations on the Genus AcUaina, De Koninck, with 

 Descriptions of British Species, and of some other Carboniferous 

 Gastropoda." By Miss J. Donald, of Carlisle. (Communicated by 

 J. G. Goodchild, Esq., F.G.S.) 



The author makes some preliminary observations on the genus 

 Aclisina, and considers it advisable to regard A. pulchra as the 

 type of the genus, wdiile the so-called A. striattda must be placed 

 among the Mai-chisonice, and A. nana is placed in a new genus. 

 The author gives a diagnosis of Aclisina, De Kon., belonging to 

 the family Turritellidse, and describes the British species, twelve of 

 w^hich are new, including two new forms placed in a subgenus. 



Of the family Murchisonidse, and in the section Aclisoides of 

 the genus Murchisonia, the form of A. striatula, De Kon., and a 

 variety are described ; and a diagnosis of the new genus, in which 

 A. nana of De Koninck is placed, is given, followed by a description 

 of the species. 



IL— December 1, 1897.— Dr. Henry Hicks, F.R.S., President, in 

 the Chair. The following communications were read : — • 



1. " A Eevindication of the Llanberis Unconformity." By the 

 Eev. J. F. Blake, M.A., F.G.S. 



In a paper published in the Quarterly Journal of the Society 

 for 1893, the author of the present paper maintained that certain 

 conglomerates and associated rocks occurring for some distance 

 noilh-east and south-west of Llauberis, which had hitherto been 



