Abstracts of Papers read on Geology. 465 



limestones, is supported by the character of the sandstones. These 

 at their base often contain abundant pellets of marl, which from their 

 form appear to have been sun-dried and so rendered sufficiently 

 coherent to be capable of transportation for short distances without 

 losing their cuboidal form. The phenomena suggest formation in 

 shallow water, during a dry epoch, subject to sudden or periodical 

 floods. 



(13) The Geology of the District between Abeeeiddt and Pencaee, 

 Pembeokeshiee. By A. Hubeet Cox, M.Sc, Ph.D., F.G.S., and 

 Professor 0. T. Jones, M.A., D.Sc, F.G.S. 



IN an introductory paragraph the authors referred to the work of 

 previous observers, namely, Hicks, Reed, EUes, and Elsden, and 

 to the visit of the Geologists' Association during Easter, 1910, when 

 results were obtained which suggested that this area required re- 

 investigation. Examination by the authors has proved that the 

 apparent sequence is extremely complicated by strike-faulting, and 

 instead of Llandeilo and Bala rocks as previously supposed, Arenig 

 and even Cambrian rocks form large areas of the coast. 



Part I. Abereiddy Bay to Pwll Strodyr (A. H. Cox). 



The ground is occupied by the under-mentioned beds, the strati- 

 graphical order of which is, so far as known, as follows : — 



Bala Limestone of Eastern Quarry, Abereiddy = Mydrim 



Limestone of Carmarthenshire. 

 Llandeilo .... Lower Dicranograptus Shales = Hendre Shales of 

 Carmarthenshire. 

 TDidymograptus Murchisoni Shales. 

 J J Didymograptus Murchisoni Volcanics (including the 



■ j Abereiddy Ash, and Llanrian lavas). 

 iDidymograptus bifidus Shales. 



{Tetragraptus Beds — dark slates. 

 Perth Gain Beds — grits and slates with Orthis calli- 

 grainma, var. proava. 

 Abercastle Beds — sandy mudstones with Ogygia 

 selwyni, etc. 



? gap. 

 rCastell Coch Beds — cleaved blue-black mudstones. 

 Doubtful Age . . \ Ynys Castell Beds — siliceous mudstones and cherts. 

 vYnys Castell grit and breccia. 

 ? break. 

 LiNGULA Flags . . Flags and laminated quartzites with imgMZeZZadawsn. 

 Doubtful Menevian. Slates near Abercastle with Agnostus sp. 



The ' Middle Llandeilo ' of Hicks' classification has been found to 

 include the Lower Dicranograptus Shales and the succeeding limestone ; 

 that is, actually more than the Llandeilo formation as now defined. 

 The ' Upper Llandeilo ' includes various Lower Llanvirn and Arenig 

 beds ; the affinities of the other rock-groups are briefly discussed in 

 the paper. Lingula flags occupy muck of the adjoining inland 

 district. 



References are made to certain ''intrusive rocks and their relation 

 to the adjoining sediments". The detailed mapping of the area is 

 now in progress. 



DECADE V. — VOL. X. — NO. X. 30 



