Xxvlli FLORA OF BERKSHIRE 



Dipsacus sylresfris, Juncus glaucufi, Equisetiim maximum, Scirpus sylvatlcus, 



Carex pendula, Paris quadrifulia, Centaurea nigra, Cnicus xxilustris, and Pxdi- 



caria dyseni erica. 



The Corallian Beds, when fully developed, fall into the following 



divisions : — 



Upper Calcai'eous Grit. 



Coral Rag. 



Lower Calcareous Grit. 



The Lower Calcareous Grit consists of sands, frequently incoherent. 

 But portions are liable to be bound together by a calcareous cement, 

 so that we find, intercalated in the lower material, beds and large 

 nodular masses of hard cal'^areous sandstone. 



The Coral Rag is mainly limestone. Here and there it includes 

 small Coral reefs, with the corals still in the position in which they 

 grew. Other portions consist of rolled and worn fragments of various 

 calcareous organisms. Bands of Clay also occur. 



The Upper Ccdcareous Grit is scarcely recognizable in the county. 



The country occupied bj^ the Corallian Beds forms a plateau rising 

 in a low escarpment on the north above the Oxford Clay, and with 

 a gentle slope to the south. The soil is light and open, sandy or 

 rubbly according as sand or limestone forms the bed rock. The 

 district is much more thickly populated than that of the Oxford 

 Clay and contains many villages. On the houses and walls Sedum 

 dasiip)hyllmn maybe found, and is locally abundant and possibly native, 

 but practically restricted to this area. Along the northern and 

 eastern escarpments many small valleys cut through the Corallian 

 Beds down to the Oxford Clay, and these are the homes of many local 

 bog and marsh plants. The Corallian Beds are bounded on the south 

 by the low flat tract of Kimeridge Clay, except about Faringdon, 

 where the Greensand rises from the upper surface of the Coral Rag. 

 The Coralline Oolite occurs as a very narrow strip at Faringdon, but 

 broadens out so as to embrace the whole of Buckland Cover, and 

 stretches as far south as Fyfield and Frilford, where it retreats north- 

 wards by Sandford and Cumnor, and from that place forms only 

 a narrow band above the Oxford Clay. From North Hinksey to 

 Rushmead Copse near Radley the formation exists as a narrow indented 

 band, gradually descending to the south at a dip of about i° till it 

 reaches the bed of the Thames, where it is overlaid with low-level 

 gravel. A similar narrow band extends above the clay round the 

 headland of Wytham. Near Marcham the formation is fossiliferous 

 and yields fine specimens of Ammonites perar^natus together with TIemepe- 

 dina Marchamiensis. At Wytham the formation rises as an outlier to 

 a height of 538 feet. Extensive quarries were worked in it at Wytham, 

 and there are others at Cumnor, &c. On the south the Corallian Beds 



