292 JURASSIC. 



De la Beche observed on the top of the hill between Holwell and 

 Leighton, oyster-shells of the date of the Inferior Oolite, adhering 

 to the old surface of Carboniferous Limestone, which was oc- 

 casionally pierced by Lithodovius} 



Near Bruton the Inferior Oolite is exposed in the railway-cutting 

 west of the station, and in many pits, between the town and Castle 

 Cary. Rhynchonella spinosa is abundant in this neighbourhood, and 

 here, as well as at Bath, it occurs low down in the Inferior 

 Oolite.^ 



The two well-defined divisions of the Inferior Oolite of the south 

 of England are thus described by Dr. Holl : ^ — 



Upper Ragstone, consisting of light-coloured, coarse-grained, thin-bedded or 



flaggy oolite, containing few fossils, and those chiefly in the form of 



casts (near Bath, etc.). 

 Laiver Ragstone, consisting of hard, brown, ferrruginous limestone, often 



much speckled with ovoid grains of peroxide of iron, and abounding in 



fossil remains. 



Broadly speaking the upper beds correspond with the zone of 

 Am7no7iitcs Parkiusoni, the lower beds comprise those of A. 

 Hiwiphn'csianus, etc. Such is the case in Dorsetshire and parts of 

 Somersetshire, although the beds vary to some extent, and the 

 zones are not always to be identified. Much discussion has taken 

 place concerning the correlation of the beds by Dr. Wright and 

 Prof. J. Buckman, but more recent work, especially that of Mr. 

 S. S. Buckman, has made it clear that the four Ammonite zones are 

 developed in the neighbourhood of Sherborne and Yeovil, and that 

 the ' Dorsetshire Cephalopoda-bed ' is part of the Inferior Oolite, 

 the representative of the Gloucestershire Cephalopoda-bed being 

 the upper part of the Yeovil and Bridport Sands that underlie the 

 Inferior Oolite.* (See p. 288.) 



The quarries in the neighbourhood of Sherborne and Yeovil 

 have long been known to collectors, for the beds are rich in fossils. 

 It is, however, very remarkable, as shown by Mr. S. S. Buckman 

 and Mr. Hudleston, that the fossil-beds occur at different horizons 

 in different localities. Thus at Oborne the zone o{ A. Humphries- 

 ianus is the richest bed, while at Bradford Abbas and Half-way 

 House this zone is hardly represented, and the zones of A. Parkiu- 

 soni, A. Soiverbyi, and A. Murchiso}2cr. yield the fossils. At Bradford 

 Abbas Terehratula Moricri was discovered by Mr. J. F. Walker at 

 the base of the zone of A. Parkiusoni. At Oborne Am?>iouites 

 Sauzci IS found below the zone o^ A. Humphricsiauus in a layer 

 termed the Sanzei-ho-di ; the upper part of that zone has been termed 

 the Cadomcusis-hQdi, from the occurrence in it oi A. Cadomcnsis? 



The following section of the East Hill Quarry at Bradford 



1 Mem. Geo!. Survey, i. 289. 



^ See Sir W. V. Guise, Proc. Cottesw. Club, ii. 170. 



3 Q. J. xix. 306. 



* Q.J. xxxvii. 588. 



6 W. H. Hudleston, P. Geol. Assoc, ix. 193 ; Walker, G. Mag. 1S78, p. 552. 



