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This Etage C or primordial zone proved afterwards to be the equivalent of those subdivisions of the Cambrian groups which have been above described under the names of Menevian and Lingula Flags. The second fauna tallies with Murchison's Lower Silurian, as originally defined by him when no fossils had been discovered below the Stiper-Stones.
Blind trilobites are also found as well as those which have the largest eyes, such as Microdiscus on the one hand, and Anoplenus on the other. Older than the Menevian Beds are a thick series of olive green, purple, red and grey grits and conglomerates found in North and South Wales, Shropshire, and parts of Ireland and Scotland.
FOREIGN. Ungulite or Obolus grit of Russia. BRITISH. Tremadoc slates. FOREIGN. "Primordial" zone of Bohemia in part, with trilobites of the genera Paradoxides, etc. BRITISH. Menevian beds of Wales, with Paradoxides Davidis, etc. FOREIGN. Lower portion of Barrande's "Primordial" zone in Bohemia. BRITISH. Fundamental gneiss of the Hebrides? FOREIGN. Labradorite series north of the river St.
One-tenth natural size. Menevian beds. St. Immediately beneath the Lingula Flags there occurs a series of dark grey and black flags and slates alternating at the upper part with some beds of sandstone, the whole reaching a thickness of from 500 to 600 feet. These beds were formerly classed, on purely lithological grounds, as the base of the Lingula Flags, but Messrs.
David's in South Wales, and near Dolgelly and Maentwrog in North Wales. More than forty species have been found in them, and the group is altogether very rich in fossils for so early a period. The Swedish fauna, presently to be mentioned, will be found to be still more nearly connected with the Welsh Menevian.
Classification of the Cambrian Group, and its Equivalent in Bohemia. Upper Cambrian Rocks. Tremadoc Slates and their Fossils. Lingula Flags. Lower Cambrian Rocks. Menevian Beds. Longmynd Group. Harlech Grits with large Trilobites. Llanberis Slates. Cambrian Rocks of Bohemia. Primordial Zone of Barrande. Metamorphosis of Trilobites. Cambrian Rocks of Sweden and Norway.
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