The rocks which undoubtedly occupy the lowest place in the geological formations of the Birmingham district are those crystalline and partly schistose masses which form the core of the Malvern Hills; and certain well-marked volcanic rocks which occur at the Wrekin and Nuneaton, and which appear to have their equivalents in the great igneous series of Charnwood Forest. That all these more or less crystalline rocks are of higher antiquity than the Upper Cambrian of Wales is demonstrated by the fact that fossiliferous rocks containing Cambrian fossils of this age overlie them, while the lowest recognisable zones of these overlying fossiliferous rocks (the Hollybush sandstone of the Malverns, the quartzite of the Wrekin, and the Hartshill quartzite of the neighbourhood of Nuneaton) are in part composed of their fragments. Whether, however, they belong in part to the Middle or Lower Cambrian, or wholly appertain to the earlier formations of the Archean, must as yet remain an open question. (_a._) MALVERN HILLS.--The core of the Malvern Hills is composed of a coarse syenitic, and more or less gneissose rock, pierced by veins of quartzo-felspathic rock of igneous origin (Hereford Beacon, &c). The main mass which is coarsely crystalline, becomes occasionally distinctly gneissose and even schistose, and its mineral bands strike from north-west to south-east, _i.e._, transverse to the general trend of the Malvern Ridge. The basement beds of the Hollybush sandstones (Cambrian) and the Llandovery rest unconformably upon this rock, which has consequently been claimed by some geologists as distinctly of Archean age, representing in part the Laurentian of Logan. The best localities for studying the essential characters of the Malvern rocks are the quarries of the North Hill and the Wych, and the eastern slopes of the hills between Malvern Wells and Herefordshire Beacon. (_b._) THE WREKIN.--The core of the beautiful hill of the Wrekin is formed by a magnificent series of highly acidic volcanic rocks--rhyolitic lavas and ashes. As first pointed out by Dr. Callaway, they rise out unconformably from below fossiliferous rocks of Upper Cambrian age. (Hollybush Sandstone and Shineton Shales) and are believed by him to be of Archean age. The finest exhibitions of the volcanic ashes of the group are met with in quarries on the flanks of the Wrekin itself, while the rhyolitic lavas occur in scattered localities along the hill. A broad mound of the same igneous series rises out from below the Triassic to the south of Walcot Station, and a most beautiful and instructive section of banded and spherulitic rhyolites is shewn in the quarry at the locality known as the Lee Rock.