The discovery by Professor Reynolds in the Mendips strata representing the greater portion of the Silurian succession (Rep. Brit. Assoc. Portsmouth, 1911), showing no similarity to the slates of Mortehoe and the neighbourhood, has rendered it more difficult than ever to accept the attribution by Dr. Hicks of the latter rocks to the Silurian period (Q.J.G.S., vol. lii, p.254, 1896); and now an important fact has come to light which appears to afford decisive evidence on this question.