Page:The history of Little England beyond Wales and the non-Kymric colony settled in Pembrokeshire.pdf/27

 LITTLE ENGLAND BEYOND WALES.

CHAPTER I.

PRIMARY AND PLEISTOCENE PEMBROKESHIRE.

Rocks of Pembrokeshire — Pre-Cambrian — Cambrian — Silurian — Devonian — Carboniferous — Drift — Ice Scratches — Bone Caves — Great Pleistocene Subsidence — Hoyle's Mouth — The Little Hoyle — Black Rock Caves — Caves on Caldy Island — Pleistocene Fauna — The Northern Temperate and Southern Groups — List of Caves and their Contents.

Little England beyond Wales is essentially an ancient land. It had been solid ground for untold æons, while the greater part of Europe was still sludge lying on the sea bottom. The rocks of West Wales belong either to the Primary system, or to those igneous and metamorphic intrusions which, as lava or volcanic ash, have been forced from below.

With the exception of the North American Laurentian and Huronian rocks, no recognized formation ante-dates certain fossiliferous Pre-Cambrian beds found in the neighbourhood of St. David’s, and consequently called Menevian by Dr. Hicks, who drew the attention of geologists to them. In these are to be found the earliest crustaceans, among them the queer-looking Paradoxides Davidis, a primordial trilobite that looks like a cross between a lobster and a wood-louse. This is one of the largest of the trilobites. These eatly crustaceans are found in the Cambrian which follows the Menevian, and is well represented in Pembrokeshire. In the Llandilo beds of this great system we find Graptolites at Robeston Wathen: these are a serrated sertularian family, and take their name from the resemblance their fossil bodies bear to writing in some unknown character. At the same place we find the allied Didymograpsus; at St. David’s are worm tracks, and the trilobites known as Calymene and Ogygia Buchii; while at Gilfach, near Narberth, is a quarry filled with specimens of the great Asaphus tyrannus on such a gigantic scale, and in such profusion, that they would provide a young geologist with dream subjects for the remainder of his life. In a cutting near Haverfordwest, on the South Wales Railway, which passes through the Bala beds, the coral-like Petraia vivia, and the bivalve Strophomena depressa, are found in bewildering numbers. This has led us over an almost imperceptible borderland into the Silurian system. Good specimens of the Llandovery beds are to be seen at Marloes, on the extreme south-western point of the county, and the Wenlock rocks crop up at Talbenny, not far off. Superimposed on the Silurian lies the Devonian.

This period is remarkable, in that at length we reach terra firma; for although the Devonian is par excellence the fish period, yet among its fossils are indubitable remains of land plants: horse-tails, club mosses, ferns, and conifers. In Laurentian, Huronian,