On Bolopora undosa gen. et sp. nov.: a Rock-building Bryozoan with Phosphatized Skeleton, from the Basal Arenig Rocks of Ffestiniog, (North Wales)

Publisher Website
Google Scholar
Abstract
In the course of many years' map-making and searching for fossils among the cleaved and altered Cambrian and Ordovician rocks which compose the Moelwyns and the Manod, and the Slate-Belt of Blaenau Ffestiniog, Prof. W. G. Fearnsides has noted the almost general occurrence of streaks and nodules of some dark fine-grained, banded, chert-like material in the basal part of certain conglomeratic lenticles or beds, at or near the surface of discordance where Tremadoc and Arenig rocks adjoin, that is, in the lowest layers of the so-called ‘Garth Grit’. In 1913, when Prof. E. J. Garwood gave his Presidential Address on ‘Algæ as Rock-Builders’ to Section C at the Birmingham Meeting of the British Association, Prof. Fearnsides exhibited specimens of the nodular material which he had collected from the basal layers of the Garth Grit exposed in the cliff at the head of Cwm Bowydd, 100 yards south of the new hospital at Blaenau Ffestiniog, and from Bryn Glas. At that time, Prof. Fearnsides had recognized that the micro-structure of the nodules afforded evidence of their organic origin, and suggested that they had been built up by algal incrustation upon a grit or pebble base. As, however, biologists were unable to discern any real resemblance between micro-sections of the nodules and those of algae, no interpretation of their structure was at that time forthcoming. Since the Birmingham B.A. Meeting, quarrymen, endeavouring to exploit an unproved vein of slate at Bryn Glas, west of Llyn Morwynion, have opened further chambers in the

This publication has 0 references indexed in Scilit: