Geology of Wiltshire. 331 



of Mollusca, plates and spines of Echini, stems of Penfacrini, 

 and fragments of plants strewn over the surface of the slab. 

 Strata of this kind will be found in the quarries at Bicker's 

 Barn and West Yatton near Corsham, the Folly north of Tetbury, 

 in the quarries around Shipton Moyne, at Dudley House near 

 Araney, and in quarries at Barnsley. The finest sections of this 

 formation are exhibited in the railway cuttings at Corsham and 

 Kemble. 



In the neighbourhood of Tetbury and Cirencester, we find beds 

 of yellow siliceous sand, containing large blocks of chert, a hard 

 siliceous limestone which, on being split, seldom shows the concre- 

 tionary structure. These masses may be seen in a quarry near 

 Sandy Lane, south of Cirencester, of which the following is a 

 sketch. 



No. 3. 



Forest Marhle near Cirencester. 



a Slaty, false-bedded oolite, witli oysters. 



b Soft yellow sands, with large blocks of chert. 



This bed of sand occurs also at Chavenage Green, north of 

 Beverstone, and at Hillsome near Tetbury. The entire thickness 

 of the Forest marble around Tetbury is about 60 feet, which 

 becomes diminished to more than one half towards the north-east 

 extremity of the district.' 



1 The Forest Marble is well developed at Atworth, near Melksbam. It is 

 here worked for tile, stone and rough walling purposes. It contains many 

 fossils, and the palates of Acrodus and other fish, (called by the quarrymen 

 leeches,) are abundant. Near the residence of Sir John Awdry, at Xotton, are 

 several quarries of Forest Marble. Sorae of these contain beds of sharp 

 siliceous sand, and exhibit very interesting examples of false bedding, and of 

 the remarkable way in which these shifting beds of sand were borne about by 

 the waves and tides during the deposition of the stratum. The railway sec- 

 tions la this neighbourhood are also very interesting. 



