A HISTORY OF HEREFORDSHIRE discovered fragments of a peculiar limestone containing minute organisms which Mr. F. Chapman pronounced to be foraminifera. The Polymorphina-Lapworthi Zone Professor Groom regards as the top- zone of the Middle Cambrian, and that characterized by Sphaerophthalmus alatus — namely, the Lower and Upper Black Shales and the sedimentary deposits associated with the intervening igneous band — as the top zone of the Upper Cambrian, holding that the Dictyonema, or Bronsil Shales, are best grouped with the Ordovician. The Grey Shales have been divided into four zones by Professor Groom, namely, in ascending order: (i) The ' Middle' Igneous Band, (2) Lower Grey Shales, (3) Coal Hill Igneous Band, and (4) the Upper Grey Shales. Symonds was the first to discover Dictyonema sociale in these shales, and thereby to demonstrate their great antiquity. The neighbourhood of Coal Hill is very picturesque, but the name perpetuates the memory of a ridiculous search for coal in the Cambrian Shales — beds which were formed millions of years before the coal ! The igneous rocks associated with the Malvern Cambrian Beds, accord- ing to Professor Groom, are all intrusive and of pre-May Hill Sandstone date.^ Formerly it was held that the majority of the sills and dykes were con- temporaneous, but a number of views have been expressed on the matter by those who have worked them. Professor Watts thinks that ' while certain of the rocks are of this date [pre-May Hill Sandstone], some of the series, as elsewhere, may be younger.' " The Cambrian Beds, which are exposed in the lane at Pedwardine on the north-western limits of the county, belong to the Shaly Division and correspond to the Shineton Shales of Shropshire and to the Dictyonema Shales of the South Malverns." Ordovician System Between the Cambrian and the Silurian should come the Ordovician, but in the South Malverns and at Pedwardine the Upper Llandovery rests directly upon the Dictyonema Shales — the whole of the Ordovician, and the Lower Llandovery, are absent. In these parts, therefore, either the Ordo- vician and Lower Llandovery Beds have not been deposited at all, or they have been deposited in part or whole and subsequently removed. As far as is known at present the former alternative seems the more probable. As has already been mentioned, in the latest Cambrian times a land surface, probably an island, was found in the Midland and Border counties. Its western coast-line ran from somewhere near May Hill to the north- eastern confines of the county, but then swept westwards to Old Radnor, before turning northward to include in its land-mass the uplands of the Longmynds. Silurian System Above the Cambrian Shales, both in the South Malverns and at Ped- wardine, is the May Hill Sandstone. This succession shows that at the time " Quart. Jout-n. Geol. Soc. Ivii (1901), pp. 156-83. ■« Proc. Geol. Assoc, xix (1905), p. 180. " Quart. Jeum. Geol. Soc. xxxiii (1877), p. 659 ; Trans. Woolhope Nat. F. C. 1882 (1888), p. 197.
