THE CORALLIAN ROCKS OF ENGLAND. 283 



but where they are large the calcareous matter renders it more com- 

 pact. Among these shell-masses are here and there masses of coral, 

 the only ones found in situ in this district. The commonest is a 

 species of Stylina, in masses about six inches in diameter ; and 

 there are also portions of Thamnastrcea. The shells are Cerithium 

 muricatum, C. Pellati (De Lor.), Acteonina miliola, Merita minuta, 

 Natica clio, Astarte polymorpha, Gastroclicena carinata, Trigonia 

 (clavellate), Tancredia planata,Pecten qualicosta, P. lens, and probably 

 many more. Although this can scarcely be called a " coral rag," it 

 is the nearest approach to it that we have yet seen ; but the cha- 

 racter of the fauna leads us to the belief that it is probably older 

 than the CoralRag of the period of Cidaris florigemma, though pos- 

 sibly not far removed in age from the Trigonia-heds of Weymouth. 

 The uppermost beds throughout this neighbourhood are similar 

 shell-beds, with the fossils included in the above two lists, with the 

 addition of Ammonites plicatilis and Cucullcea corallina, associated, 

 where the group is cut off by a fault to the north, with thick beds 

 of blue calcareous grit. 



Such are the calcareous beds of this district. Of the overlying 

 sands and grits, the glimpses are few and far between. We have 

 found no exposures of them between the oolites and the Kimmeridge 

 Clay, except at the spot mentioned and from Gillingham northwards. 

 Their intermediate position and their fossils at Sturminster mark them 

 plainly as comparable with the Sandsfoot series, proving that 

 towards the end of the period, if not before, there was some 

 community between the two areas. A representative of these 

 sands and clays to the north of Gillingham is generally seen as a 

 comparatively thin covering of ferruginous semi-earthy material mer- 

 ging gradually into the quaternary soil, and lying on the waterworn 

 edges and in the cracks of the sandy oolites and shell-beds, showing 

 a distinct interval of time between them, and incidentally proving 

 the early age of the former. In some places, however, this material 

 is itself a remanie deposit, having fragments of rolled oolitic iron- 

 stone interspersed in layers in the clay. The contained fossils are 

 Phasianella Coquandi, Belemnites nitidus, Exoggra nana. 



Comparing this district generally with the Weymouth area, we 

 find similarities and differences. They are similar by the great 

 variety of calcareous beds intervening between the sandy series 

 above and below, by the reduction of corals to a minimum and the 

 substitution of rubbly beds, also by the presence of false-bedded 

 limestones. They differ by the former containing a much smaller 

 development of arenaceous material, by the abundance of pisolite, 

 and by the general massiveness of the middle beds. 



III. The North- Wiltshiee, Berkshire, and Oxeordshire Eange. 



The area of Corallian rocks on which we now enter, though con- 

 tinuous by some part of the series from one end to the other, is so 

 long and narrow, and presents so many minor areas that have 

 distinctive characters, that we cannot treat it as a whole as we 

 have done the two former districts, but must divide it into sections 

 geologically connected. Among these are included: — the classic 



