154 Geological Society : — 



Mr. E. Williamson had proved the correctness of their opinion that 

 the strata at Tyddynglwadis belong to the Primordial zone, and 

 that, within a limited area extending east from the boundary line of 

 the Lower Cambrian grits, the rocks ought to yield a series of 

 fossils of Primordial types. This examination had also enabled 

 them to draw a section extending from the junction of the Lower 

 and Upper Cambrians at Cefn Ddiddw to the base of Craig-y-Dinas, 

 which was described in detail by the author, who adopted the fol- 

 lowing division of the beds : — 



Lower Cambrians or Harlech Grits. feet. 



Lower Linsula-beds / Tyddynglwadis slates 1,136 



Upper 



\ C wmheisian slates 2, 500 



Cambr'a i Middle Lingula-beds Hafod Owen sandstones ... 5,000 



' (upper Lingular {Sr&^L:::::::: } ^ 



10,136 

 June 6, 1866.— Warington W. Smyth, Esq., M.A., F.R.S., 



President, in the Chair. 

 The following communications were read : — 



1. " On the Metamorphic and Fossiliferous Rocks of the Co. 

 Galway." By Prof. R. Harkness, F.R.S., F.G.S. 



A great portion of the area under consideration was described as 

 being occupied by contorted gneissose rocks, striking east and west, 

 with a prevailing southerly dip towards the granitic area of Galway 

 Bay. Quartzose rocks exhibiting great folds give rise to the bold 

 mountainous scenery of Connemara ; and reposing on these, and 

 passing underneath the gneissic strata, is a band of serpentinous 

 limestone, the structure of which is not of animal origin, but results 

 solely from mineral association. The gneissose rocks on the north 

 are covered unconformably by sandstones, the fossils of which indi- 

 cate the horizon of the Upper Llandovery Rocks. These meta- 

 morphic rocks correspond with those of the Highlands of Scotland, 

 representing the Upper Quartz rocks, Upper Limestone, and Upper 

 Gneiss, the positions of which are known in consequence of the 

 Lower Limestones at Durness having been determined to be not 

 lower than the Llandeilo Flags. 



2. " On the Metamorphic Lower Silurian Rocks of Carrick, Ayr- 

 shire/' By J. Geikie, Esq. 



In surveying the southern district of Ayrshire, the author and his 

 colleagues recognized the metamorphic character of certain Diorites, 

 Serpentines, and crystalline felspathic rocks independently of each 

 other ; and Mr. J. Geikie had also been enabled to trace passages 

 between the various altered rocks, which seemed to him to throw 

 light upon the obscure process of metamorphic action. In this 

 paper he first gave a generalized description of the metamorphic 

 strata, dividing them into four groups — namely (1) Felspathic 

 Rocks, (2) Diorites, (3) Serpentines, and (4) Altered Limestone 

 and Calcareous Greywacke, — and again subdividing the Felspathic 

 rocks into Amygdaloid, Porphyry, Brecciasform rocks, and finely 

 crystalline Felstones, and the Serpentine into Schistose and Com- 

 pact. He also described the association of serpentine with diorite, 



