GEOLOGY nevertheless, has mapped them in great detail, together with the numerous igneous rocks with which they are pierced. Where these intrusive igne- ous rocks occur in the Shale Division they give rise to ground of a very hummocky appearance. South Maherns. — ^The arenaceous rocks were called by Professor J. Phillips in 1848 the Hollybush Sandstone, but their presence had been noted before that year by Murchison and De la Beche. H. B. HoU searched them for fossils, and endeavoured to determine the true succession of their com- ponent beds ; " but little really detailed work was accomplished until Professor Groom undertook their investigation. He described the Malvern Quartzite,^* portions of which are conglomeratic containing fragments of Malvernian and Uriconian rocks, and this shows that a land-surface containing both these rock-types was being denuded at the time of formation of these basal beds." Such conglomerates were noticed by Horner, Murchison, Phillips, Holl, and Symonds ; but Professor Groom does not think that any of the patches of this rock now visible are of the very lowest beds, holding that all the present junctions are fault-planes. The Malvern Quartzite is interesting as being the only Quartzite of this stratigraphical position that has afforded traces of organic remains other than worm-tracks ; but it is well to bear in mind that the Quartzite after all is only Hollybush Sandstone cemented firmly together by infiltrated -silica, and may possibly be of slightly later date than is usually supposed. The Hollybush Sandstone comprises Sandstones which are massive- bedded in the upper portion ; but more flaggy, and with shale-partings, in the lower. There are few good exposures of these beds ; the best is that in a quarry on the south side of the Ledbury and Tewkesbury Road before it enters the Hollybush Pass from the west. The representatives of the Shaly Division occupy a roughly semi-lunar area, extending from near the Obelisk in Eastnor Park to the Raggedstone, where they are faulted against the plutonic rocks of the range. They consist of black and grey shales, called by Phillips the ' Malvern Shales ' ; but by Holl after their colour — the ' Black Shales ' and the ' Grey Shales.' They are veined with intrusive igneous rocks; not contemporaneous, as has usually been taught. For the terms ' Black ' and ' Grey Shales ' Professor Groom has substituted the names ' White Leaved Oak ' and ' Bronsil Shales.' Both of these Professor Groom has subdivided ; the former, in ascending order, into (i) Lower White Leaved Oak Igneous Band, of which Polymorphina Lapworthi, an ostracod, that was first discovered in this region and described by Professor Groom,^* is the zonal fossil, (2) Lower Black Shales, (3) Upper White Leaved Oak Igneous Band, and (4) Upper Black Shales. The Lower Black Shales were the oldest portion of the ' Malvern Shales ' known previous to Professor Groom's researches, and the exposures by the side of the footpath leading from the hamlet of the White Leaved Oak to Fowlet Farm, and in the fields to the north-west of the hamlet, have long been known as good collecting grounds. Associated with the rocks of the Upper White Leaved Oak Igneous Band, in the shale portion of which both Symonds and Professor Groom have found trilobites. Professor Groom " Quart. Journ. Geol. Soc. xxi (1865), pp. 87, 100. " Ibid. Iviii (1902), p. 90. " Rep. Brit. Assoc. 1900 (Bradford), p. 739. '" Quart. Journ. Geol. Soc. Iviii (1902), pp. 83-8. 7
