The two chief points of interest in the Lower Lias of Sedbury Cliff, which I examined in company with Mr. L. Richardson, are, firstly, the relation of the basal conglomerate to the Cotham Marble and White Lias of neighbouring districts; and, secondly, the examination of the faunal sequence, with a view to testing the absolute value of ammonite-zones. 1. The Conglomerate. This is composed of fragments of a very compact, lithographic, argillaceous limestone, which exhibits well-marked conchoidal fracture. The large fragments are invariably tabular and lie horizontally, their vertical dimension being small compared with their horizontal extent; all of them show internal, horizontal bands of colour which may undoubtedly be considered to have existed in the original rock-layer from which the fragments were broken. The smaller fragments lie in all directions, and many of them are rounded; they almost invariably exhibit an outer, more deeply stained shell, the colour of which shades off inward quite uniformly and imperceptibly. There can be little doubt that this staining has been produced subsequently to the breaking and rolling of the fragments, and, most probably, subsequently to their cementation into a conglomerate. That the fragments of the conglomerate once formed part of a layer exactly similar to the true Cotham Marble of the Bristol and Sodbury areas, is almost without question, since they agree absolutely in lithological characters with specimens of that rock, though I have noticed no fragments which show the peculiar arborescent markings. It is, however, important to notice that the arborescent