﻿Vol. 6 I.] SEQUENCE IK THE BRISTOL AREA. 225 



As might have been anticipated from its geographical position, 

 the section at Tytherington is most closely related to that at 

 Sodbury, both palseontologically and lithologically. 



The scarcity of Oaninia just above the resupinata-subzone, where 

 it is so abundant in the southern part of the Bristol area, is a 

 feature common to both sections, while the relative abundance of 

 the brachiopods is almost identical in the two sections. 



Again, the increase in the predominance of dolomites over shales 

 in the middle of the Carboniferous-Limestone Series which was 

 noticed in the Sodbury section is, at Tytherington, a very striking 

 feature. So massive do these dolomites become in this section 

 that the tunnel has been bored through them, and left unbricked. 



A minor feature of some interest is the occurrence of beds of 

 highly-quartzose sandstone, both at Sodbury and at Tytherington, in 

 the lower part of the JSeminula-Zojie ; at Sodbury these sandstones 

 occur at the base of S 1? while at Tytherington they occur near the 

 top of that subzone. 



(e) The Clevedon Area. 



Clevedon lies 10| miles west, slightly south, of Clifton Suspension- 

 Bridge, on the south side of the Severn estuary. 



Tournaisian. 



Exposures and lithological character: — 



I. The sequence, as exposed in ascending order along the coast, 

 from north-east to south-west, 

 (a) The Cleistopora-Zone, composed of shales and subsidiary 

 limestones, is exposed on the foreshore between the pier 

 and Clevedon Bay. 

 (h) The daihratus-subzone (massive limestone) is excellently 

 shown in the cliffs and on the foreshore, extending from 

 Clevedon Bay to a little south of Littleharp Point. 



(c) The re&upinata-aubzoiie forms the cliffs at Salthouse 



Point. 



(d) The uppermost beds of the Zaphrentis-Zone, including 



Horizon y, occur near the Pill, where specimens of 

 Zaphrentis and Caninia, washed out of the cliffs, can be 

 picked up in hundreds. 



II. The sequence, as exposed in ascending order along the path on 

 Strawberry Hill, the Carboniferous ridge which lies about 

 three quarters of a mile east of the beach, west of the road 

 from Clevedon to Portishead. Starting at the north of the 

 hill, where the Pennant Grit rests upon the Carboniferous 

 Limestone, and proceeding southward, the zones enumerated 

 below are met with in the following order : — 

 (a) The uppermost beds of the dathratus-aubzone. 

 (6) The resupinata-Bubzone, chiefly characterized by the pre- 

 dominance of Zaphrentis aff. Phillipsi (the subzonal index 

 being scarce). 



