22 GASTEROPODA OF THE INFERIOR OOLITE. 



an important influence on the Fauna. There appears to be a really large coral 

 growth in the Upper or Ragstone division of the Inferior Oolite on Dunclry Hill. 

 So far as I know, this is the only accumulation in beds of this age throughout 

 England to which the term " reef" could be fairly applicable. 



But although the remains of actual coral growth now presented to us are 

 scanty, there can be little doubt that the Inferior Oolite was deposited when a 

 considerable growth of coral existed in some places, and mostly in the direction of 

 the prolongation of the escarpment. It must of course be borne in mind that we 

 merely see the truncated ends of the beds along the line of strike, and that these 

 beds have all extended much further in a direction opposite to that of the prevailing 

 dip. Taking the Cotteswold area, for instance, as an example, the westward 

 prolongation of the Inferior Oolite from such a place as Leckhampton might, and 

 most likely did, extend over what is now the vale of Gloucester, towards the high 

 lands of the west, which would be the direction of the shore of that period. It 

 was most probably on fringing reefs connected with a shore so situated that the 

 main mass of actual coral was being accumulated. And this growing coral not 

 only fostered a peculiar Fauna, but also furnished to the waves no small amount of 

 the calcareous mud, which, in the form of paste or granules, constitutes a large 

 proportion of the Inferior Oolite as it is now preserved to us. The long east and 

 west axis of the Mendips would form an island in the Inferior Oolite sea of the 

 south-west, whilst its axial prolongations would form shallows or submarine 

 ridges such as that so well exposed at Vallis, near Frome, on which several feet of 

 a rubbly variety of the upper beds of Inferior Oolite may be seen to repose. A 

 little way off, on the north and south flanks of this Mendip island, are considerable 

 accumulations of impure calcareous sediment of Inferior Oolite age, almost devoid 

 of fossils, and yielding building stones (Freestone quarries). In Dorsetshire, on 

 the other hand, with which South Somerset may be included to a certain extent, 

 the signs of coral reef are small, and where Cephalopoda are very numerous the 

 conditions must have been very different ; but this will be seen more fully when 

 the details of the several districts are given. 



What I particularly wish to emphasize just now is the extraordinary irregularity 

 and marked contrast in the several portions of the Inferior Oolite, and, by consequence, 

 of its fossil contents. This peculiarity is on the whole favorable to variety in the 

 forms of life, or, stated in other terms, the more varied the facies the more 

 numerous will be the forms in a given series of beds. This, I think, especially 

 affects Gasteropoda, which are easily influenced by change of physical conditions 

 within a given area, such physical conditions being indicated by the nature and 

 varying volume of the deposits. 



Despite its variability and local attenuation the Inferior Oolite is nearly 

 continuous in its outcrop from Bridport Harbour on the Channel to Blue Wyke on 



