During the summer of 1890, Professor Cole and I, whilst geologising in North Wales, were led to examine the Hirnant Limestone. Since then the further examination in the laboratory of the specimens collected by myself have revealed some remarkable characteristics which, as they are as yet undescribed, I think are worthy of notice.

The specimens on which the following observations have been made were obtained from a small cutting opposite to the farm named Cwm-yr-aethnen, in the valley of the Hirnant, which descends towards Bala Lake. The limestone occurs here between two beds of fossiliferous slate. The exposure is very small, and being considerably overgrown, it was only by careful search that we succeeded in finding it. The Survey Memoir mentions that an. outcrop occurs at Trum-y-gwrageda, and also that loose blocks were found by Sedgwick at the Bwlch-y-groes; but after a careful search we failed to find it at either of these localities.