ROCKS OF SOMERSET AND DEVOX. 377 



(1). Variegated marls occasionally containing arenaceous beds. 



(2). Sandstones, or rock sands, apparently forming the marginal 

 deposit, marking, with few exceptions, the first stages of deposition 

 in these areas, passing upwards, in places, by intercalation into the 

 overlying marls, at AVembdon passing downwards into hard bedded 

 breccio-conglomerate. 



If the Wembdon breccias should prove persistent beneath the sand- 

 stones in the Bridgewater district, a threefold division of (1) marl, 

 (2) sandstone, (3) breccia, would be necessary, presenting some 

 slight affinity to the (1) marls, (2) sandstone, (3) dolomitic con- 

 glomerate flanking Broadfield Down (to the north of the Mendips). 



III. West-Somerset and Devon Area. 



The area now to be treated of is bounded on the north by the 

 Bristol Channel, on the south by the English Channel, whilst the 

 Quantocks, Taunton Yale, and the Blackdown range form a provi- 

 sional boundary on the cast: the Devonian and Culmiferous highlauds, 

 stretching south from the Brendon Hills, define its western limits. 



Muck has already been written about the Trias of Devon as 

 shown in its greatest exposure on the south coast. The whole 

 section has been described by Mr. Pengclly, and attention has been 

 specially directed to individual divisions, to the marls and sandstones 

 between Exmouth and Straight Point by Mr. Ormerod, to the Pebble 

 beds of Budleigh Salterton by the late Mr. Salter and my friend 

 Mr. Yicary of Exeter, to the Upper Sandstones by my friends 

 Messrs. Lavis and Whitaker ; so that in the following brief notice 

 my object is rather to prove the maintenance over the area under 

 consideration of the sequence observable in the south-coast section, 

 and to observe the relations of the beds in that section, than to 

 attempt any detailed account of the lithological characteristics of 

 separate' divisions. Inasmuch as one section of any set of beds, be 

 it ever so clear, cannot be taken without further research as the 

 absolute and unvarying type of the whole, I propose, by the cor- 

 relation of the beds in four distinct parts of the area and by a 

 glance at the structure of each, to endeavour to prove the persistence 

 of the south-coast divisions throughout the area, and that any hiatus 

 is rather due to concealment by faults or overlap* than to impersist- 

 ence, and, whilst showing the difficulties in the way of forming esti- 

 mates of their thickness through the prevalence of faults repeating 

 and (in some cases) cutting out the beds, to attempt an approxi- 

 mation to the thickness of the several divisions. 



I made my first acquaintance with the Trias of this area at 

 Wellington, in the year 1871, and was then led to make, with one 

 exception, the same divisions as are displayed in the South-Devon 

 coast. In the year 1872, the division underlying the conglomerates 

 was indecisively indicated; but the discovery of its true character in 

 the following year necessitated a reinvestigation of its boundaries, iu 

 doing which considerable light was thrown upon the relations of 



* By the term overlap no unconformity is here meant, but the conceal- 

 ment of lower beds by the extension, through a progressive subsidence, of those 

 next in time upon the old rocks. 



