A Manual of Elementary Geology / or, The Ancient Changes of the Earth and its Inhabitants as Illustrated by Geological Monuments

by Sir Charles Lyell

Tentaculites scalaris, Schlot. Eastnor Park; nat. size, and magnified.

The most ancient bony remains of fish yet discovered in Great Britain are those obtained from the Wenlock limestones; but coprolites referred to fish occur still lower in the Silurian series in Wales.

Fig. 429.

Ogygia Buchii, Burmeister. Syn. Asaphus Buchii, Brong. ¹/₄ nat. size. Radnorshire.

2. The Llandeilo flags, so named from a town in Caermarthenshire, form the base of the Silurian system, consisting of dark-coloured micaceous grit, frequently calcareous, and distinguished by containing the large trilobites Asaphus Buchii and A. tyrannus, Murch., both of which are peculiar to these rocks. Several species of Graptolites ([fig. 430.]) occur in these beds.

Fig. 430.