462 



THE GEOLOGIST. 



abruptly from the low ground of the Oxford Clay, and overlooking the 

 valley of the Isis. In a large quarry, at Kingstone Bagpuze, the Upper 

 Grit may be observed resting on the Coral Rag, which in its turn reposes 

 on the Lower Grit. At Wheatley, to the north-east of Shotover, these 

 beds form an anticlinial, or dome, dipping under the Kimmeridge Clay, in 

 every direction from the centre. The Coral Rag, in this neighbourhood, 

 contains its usual assemblage of zoophytes and echinoderms. The Kim- 

 rneridge Clay extends along a band of country following the course of the 

 Coral Hag, and resting upon the southerly slope of the terrace formed by 

 that rock. Its organic remains do not offer any important differences from 

 those of the Oxford Clay ; indeed, many of them are common to both for- 

 mations. The best sections of the Kimmeridge are at Headington, near 

 Oxford, and Culham, near Abingdon. The Portland beds extend in a 

 narrow band round the Shotover ridge of hills. At Combe Wood, near 

 Cuddesden, a small patch of Purbeck beds may be observed resting on the 

 Portland Stone. They consist of about four feet of grey marly limestone, 

 containing Cypris, Mytilus, and Paludina. At Culham, the Gault and 

 Lower Greensand may be observed reposing on a base of Kimmeridge 

 Clay. The Gault at this place is a blue laminated clay, with its character- 

 istic fossils, Ammonites lautus, A. interruptus, Nucula pectinata, Inocera- 

 mus concentricus, and Plicatula pectenoides. The Lower Greensand con- 

 tains no fossils in the neighbourhood of Oxford, but at Faringdon the re- 

 markable gravels of this age are almost entirely composed of sponges, 

 bryozoa, and mollusca. The freshwater sands of Shotover have been 

 the subjects of essays by several writers, who all agree as to their fresh- 

 water origin, but are not so unanimous as to their geological date ; some 

 being inclined to regard them as being the equivalent of the Hastings 

 Sands, or Wealden beds, and others as an estuarine condition of the Lower 

 Greensand. Professor Phillips is of the latter opinion, and it seems to be the 

 safer course to regard them as an exceptional condition of the Greensand. 

 They contain very few fossils ; those that have been collected belong to the 

 genera Paludina, Cyrena, Unio, and Cypris. These beds are valuable, as 

 producing the well-known Oxford ochre. The high-level gravel belongs 

 to the period of the northern drift, and is so called because it occupies the 

 highest ground in the district, as at Wythani Hill, where it attains an 

 elevation of 583 feet above sea-level. It does not contain any organic re- 

 mains, and is composed of well-rounded quartz pebbles. The low-level 

 gravel is quite distinct in its origin, being formed almost entirely of local 

 rocks, and containing water-worn Oolitic fossils, such as Terebratulse, and 

 fragments of Eelemnites. South of Abingdon, where the surface-rocks 

 are cretaceous, it passes into a flint gravel, evidently derived from the de- 

 nudation of the chalk of the district. The only remains belonging to the 

 period when it w r as deposited are those of elephants, probably JElephas 

 primigeuius. From the position of this gravel, which extends into the 

 valleys of the Windrush and Evenlode, and other tributaries of the 

 Thames, we may conclude that it was formed at a comparatively recent 

 period, when the ridges of Coral Pag were dry land, and what are now 

 river-valleys were a series of shallow lochs, similar to those on the west 

 coast of Scotland. 



At the meeting of January 13th, 1863, the President, the Rev. Professor 

 Henry Griffiths, in his Address referred at length to some interesting 

 geological phenomena, peculiar to North and South Wales, with regard to 

 the Old Red Sandstone, and particular attention was drawn to that system 

 of -strata. The President then miuutely described the series of fossil ich- 

 thyolites of that age, lately added to the collection of the Royal Institu- 

 tion. 



