Geological Society of London. 417 



only occurring as a basement series, but in some cases persisting 

 continuously upwards as the marginal equivalent of the marl, as 

 Ehsetic beds overlie both alike. South of the Mendips the Trias is 

 similarly constituted, but is of much greater thickness. 



The second area embraces the country south of the Polden Hills 

 as far as a north and south line through Taunton. 



The chief portion of the Trias in this area, as in the northern, 

 consists of marls ; but unless the breccias of Wembdon, near Bridge- 

 water, are portions of a basement series, faulted up, but elsewhere 

 concealed, the lower division consists of sandstones found resting on 

 the flanks of the Quantocks, flanking outliers of the older rocks, 

 and here and there faulted up. 



In the lower parts of the marls in the Vale of Taunton and other 

 places occasional beds of sandstone are found, which from their 

 position may be regarded as equivalent to the Upper Keuper Sand- 

 stone of Professor Hull. The sandstones of this area differ from 

 the conglomerates of the Mendip country in occupying a definite 

 subordinate horizon to the marls, and not dovetailing into them. 



The third area, bounded on the north by the Bristol Channel, on 

 the south by the English Channel, on the east by the Blackdown 

 range, and on the west by the Culm and Devonian highlands, 

 presents the most complex relations of the Trias in the south- 

 western counties. 



The upper member of the series, as in the other districts, consists 

 of marls ; they contain occasionally thin beds of sandstone towards 

 the base, which may be considered, although apparently of local 

 occurrence, as Upper Keuper Sandstone. They are underlain by 

 sandstones. In these two upper divisions we have the continuation 

 of the whole Triassic series of the second area ; and in the third 

 underlying division conglomerate and pebble-beds. From Watchet 

 to a point west of Wellington this division is represented by hard- 

 bedded conglomerate, thence to the south coast by sands with 

 rounded grains and pebbles, at first of quartz grit and slate, 

 gradually giving place to the large foreign-derived quartzites of 

 Budleigh Salterton. 



A second series of marls is found to underlie the conglomerate 

 and pebble-beds conformably. This attains as much as 500 feet in 

 thickness near the south coast, but in the northern part of the 

 district does not appear to exceed 200 feet. 



The base of the series is composed of sandstone, breccia, and 

 occasionally clays, occurring at different horizons in different parts of 

 the area, and each variety locally predominant over the others. 



The clay beds appear to be confined to the neighbourhoods of 

 Exeter and Crediton. The upper part of the division south of 

 Bradninch seems to consist of red sandstones, the lowermost and 

 principal part of the division consisting of breccia. North of Brad- 

 ninch the sandstone occupies the principal portion of the division, 

 sometimes apparently to the exclusion of the breccia. Towards 

 Wiveliscombe the upper part of the series for from 15 to 30 feet 

 consists of breccia and breccia-conglomerate, the major part con- 



DECADE II.— VOL. III. NO. IX, 27 



