298 THE OXFORD OOLITE PERIOD. CHAR 



interesting and remarkable, especially ammonites,, as may be seen 

 in the Catalogue, which includes those gathered from all parts of 

 the series within the Oxonian district. This clay comes into juxta- 

 position with the Kimmeridge clay in the country north-east of 

 Oxford. Its extreme thickness, as proved by the boring at Wy tham, 

 exceeds 300 yards. The middle part, north of Oxford, yields Am- 

 monites Duncani ; the upper part, about St. Clement's, supplies 

 Ammonites vertebralis ; while between the two, in wells at Oxford, 

 we have Ammonites Lamberti. The Kelloway rock is not really 

 traceable in this quarter, but a band of septaria occurs, fifty feet 

 above the cornbrash, near Kirtlington Station, at about the place 

 of this rock, and containing some ammonites of the epoch. 



CALCAREOUS GRIT. 



Sand partly consolidated into sandstone is the basis of this 

 deposit through all the low escarpment of the tract which looks 

 northwards on the upper vale of Thames. It is rarely exposed 

 except in road-cuttings, and at the base of the ' coral rag/ where 

 that is quarried for the roads and walls. This occurs on the road 

 to Shotover, at Cowley and Bullingdon, and in the country near 

 Besselsleigh and Marcham. It is in these cases usually a fine sand, 

 with occasional shells ; the more solid parts lower down are rarely 

 found to be of use even for the rudest rural purposes. It is indeed 

 actually used on the roads at Studley, north-east of Oxford, beyond 

 which it can hardly be traced at all, till the series of these rocks 

 opens and expands in Yorkshire. Near Oxford its total thickness 

 is about 60 or 70 feet. The sand is sometimes so loose as to be 

 'quick/ and choke the wells which in many places are sunk to 

 it through the superincumbent rock and clay. This happened at 

 Even-Swindon, where a deep well through Kimmeridge clay reached 

 and penetrated the coralline oolite. Then burst up a great stream 

 of water, followed by sand in such abundance as to fill the well 

 to a considerable height. Near Abingdon, as about Marcham, it 

 is thin but fossiliferous, especially yielding many fine specimens 

 of Ammonites catena, and a solitary example of Hemipedina 

 Marchamensis. At Studley, Ammonites vertebralis, Pholadomya, 

 Modiola, Pinna, and other shells occur. 



In the railway cutting at Kennington this sand, fully exposed, 



