x. UPPER LIAS. 117 



Rhynchonella tetraedra, Terebratula punctata, Avicula novem- 

 costse, Modiola scalprum, Cardium truncatum, Cardinia crassiuscula, 

 Pholadomya ambigua, Pleurotomaria expansa, Belemnites paxil- 

 losus, Ammonites margaritatus, A. spinatus. 



UPPER LIAS CLAY. 



This deposit, which is barely traceable in a band a few feet thick 

 near Bath, and remains only a few yards thick in the southern 

 parts of Gloucestershire, swells to 80, 100, and even 230 feet in 

 the hills round Cheltenham, as for example in Leckhampton Hill. 

 In Broadway Hill it is about 100 feet, and in the country north 

 of Chipping-Norton 60 to 80 feet. From this point northward 

 the thickness varies, and at length on the coast of Yorkshire reaches 

 200 or 210 feet. 



Taking our station at Cleeve-Cloud (where the upper lias is 

 supposed by Mr. Hull to fall little short of 300 feet in thickness), 

 we may draw a line to the east-north-east, by Shipton and Daventry, 

 through Warwickshire and Northamptonshire, along which the 

 thickness may be taken at about 100 feet; and another at right 

 angles to it by Burford, along which the thickness is found to be 

 continually diminishing, so that at Stow it is 40 feet, at Taynton 

 20 feet, and at Burford only traceable as a band 6 feet thick d . 

 If the line first mentioned be prolonged to the south-west, the great 

 thickness of the upper lias is found to be rapidly diminished, so 

 that at Painswick it is about 80 feet, at Stroud 30 feet, at Wotton- 

 under-Edge 10 feet, and toward Bath a mere parting, between 

 the marlstone and the ' sand of the inferior oolite.' 



In the valley of the Evenlode, at Charlbury, the railway cutting 

 discloses the marlstone, upper lias, and inferior oolite, all much 

 reduced in thickness, in a height of 20 feet. 



The composition of the upper lias is usually very simple : a 

 nearly uniform, somewhat pale blue clay, with bands and balls of 

 calcareo-argillaceous stone, sometimes a little ferruginous, and 

 generally suited for the manufacture of cement. Balls of this sort 

 lying in the same part of the series are of some value at Whitby, 

 and yield abundance of fossils. These are usually found to have 

 been the centres of aggregation for the concretionary mud. On 



d Hull, in Memoirs of the Geological Survey, 1857. 



