TRAKSACTIONS OF SECTION C. 6.31 



reason for discarding the name Midford Sands. If the beds near Bath have not 

 proved so fossiliferous as those in other localities, there is no reason why they 

 should remain so ; for in Dorsetshire there ai-e many sections where the beds appear 

 barren, in close proximity with other exposures that yield an abundant fauna. 



2. The Relations of the Gh-eat Oolite to the Forest Marble and Fnller' s-earih 

 in the South-west of England. By Horace B. Woodward, F.G.S. 



[Communicated by permission of the Director-General of the Geological Survey.] 



The southerly attenuation of the Great Oolite, and its absence in Dorsetshire, 

 have been generally attributed to lateral changes in the strata— it being considered 

 that the Great Oolite is mainly replaced by Forest Marble (which has been stated 

 to increase in thickness southwards), and perhaps in part by the Fuller's- 

 earth. 



In Gloucestershire the Great Oolite and Forest Marble are so interblended that 

 there is no real line of demarcation. At Bradford-on-Avon this is not the case : the 

 surface of the Great Oolite, with its clusters of Apiocnnus, indicates a pause in 

 deposition, and we have locally a good line of division between this formation and 

 the Bradford Clay, which is a subordinate portion of the Forest Marble. South- 

 wards the Bradford Clay horizon extends to the Dorsetshire coast, but the Great 

 Oolite is no longer found, and we see no evidence of the Crinoid growth in sifu. 

 The estimated thickness of the Forest Marble in Dorsetshire has been much 

 exaggerated, and the evidence furnished by the persistence of the Bradford Clay is 

 opposed to the view that the Great Oolite is replaced in any way by the Forest 

 Marble. 



In Oxfordshire and Gloucestershire the Great Oolite and the Stonesfield Slate 

 merge downwards into the Fullers-earth with no marked stratigraphical division, 

 and this is the case as far as Lansdown, near Bath. Northwards the Fuller "s-earth 

 is much attenuated, and near Chipping Norton it rests on a higher stage of the 

 Inferior Oolite than we find in the Cotteswold Hills, as if in the former area the 

 conditions attending the deposition of Inferior Oolite lingered longer. Rarely do 

 we find any interblending of Inferior Oolite and Fuller's-earth ; indeed, we some- 

 times find indications of local pauses in deposition, marked by annelide burrows, &c. 

 So that on stratigraphical grounds the Fuller's-earth is more intimately connected 

 with the Great Oolite than with the Inferior Oolite. 



In Dorsetshire the Fuller's-earth series attains its greatest development in this 

 country, and is separable into Upper and Lower clayey divisions with an inter- 

 mediate bed of Fuller's-earth Eock. These divisions may be traced northwards to 

 Lansdown and Slaughterford, near Bath, where the Fuller's-earth Hock is present 

 in an attenuated form, and where the Upper Fuller's-earth merges into the base of 

 the Great Oolite. 



It is therefore clear that the mass of the Great Oolite is not represented in the 

 Fuller's-earth series of Dorsetshire, although its l&wer beds may be partially replaced 

 b\- the Upper Fuller's-earth. The mass of the Great Oolite, therefore, either 

 wedges out abruptly south of Bradford-on-Avon, or has been to some extent 

 denuded. On the whole, it appears probable that the Great Oolite has been denuded 

 — the erosion being local and contemporaneous so far as the Great Oolite series is 

 concerned. The structure of the Forest Marble, with its clay-galls, its current- 

 bedded limestones made up of broken shells and oolitic grains (the latter sometimes 

 in a sandy matrix), favours the notion that it may have been largely derived from 

 previous accumulations ; and this opinion was suggested by Dr. Sorby from a 

 microscopical study of some of the beds. 



The organic remains of the Fuller's-earth include many species common to the 

 Inferior Oolite and many common to the Great Oolite. Of seventy-two species, 

 obtained during the course of the Geological Survey, fifty-eight are known also 

 in the Great Oolite and forty-two in the Inferior Oolite, a number being common 

 to the two formations. The palseontological evidence therefore coincides with the 



