Note 172 — Chapter XII · CHARACTERS OF THE SILURIAN SYSTEM IN BRITAIN. THE ARENIG VOLCANOES
Reading edition
Mr. J. J. H. Teall, Roy. Geol. Soc. Cornwall, 1894, p. 3. Mr. L. Ransome, Bull. Depart. Geol. University of California, vol. i. p. 106.
[173] Messrs. Cole and Gregory, Quart. Journ. Geol. Soc. vol. xlvi. (1890), p. 311.