470 PllOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



study of the uj^per beds of the Keuper, the whole of the Ehsetic 

 series, and the lower marls of the blue or Lower Lias, presenting in 

 the whole about 186 beds, and attaining an aggregate thickness of 

 180 feet. The Insect and Crustacean beds are wanting at Hatch. 

 As the Lias passes towards the station it becomes very much con- 

 torted, and the beds are in the greatest confusion. The organic re- 

 mains are very similar to those at Camel, the only additions being 

 Ostrea intusstriata in the bottom bed, and Plioladomya amhigua some 

 way up. Ostrea liassica is abundant throughout the series, but^m- 

 monites planorhis is less frequent than at Camel. About 10 feet 

 above the White Lias, Avicula decussata is abundant in a bed of 

 laminated blue marl. 



The only observations necessary to make in addition to those in 

 my former paper on the Beer Crowcombe sections are, that Am- 

 monites planorhis has a wider range in them than was then indicated, 

 and that I have found Pecten Pollua; at the top of the series at this 

 place. 



Having given the above sections showing the normal condition of 

 the succession of these rocks outside the Mendips and beyond their 

 influence, I shall proceed to consider the same formations within the 

 Coal-basin — reserving for future notice an important section at Shep- 

 ton Mallet, with which it is my purpose to correlate the Sutton beds. 



3. Mhcetic and Liassic Formations luithin the Coal-Basin. — Although 

 it will be shown, as has already been done with the Keuper, that 

 the Liassic beds above the Rhaetic series present very interesting- 

 points of comparison with those noticed south of the llendips, an 

 exception to the general unconformability of these groups must be 

 made in favour of the Ehsetic series within the Coal-basin. How- 

 ever varied or unconformable may be tbe formations which the Rhsetic 

 beds separate, the constant and uniform presence of the latter in 

 the midst of so much that is unconformable is most remarkable. 

 One reason in favour of my proposal in a former paper to include 

 the " White Lias " in the Rhsetic series, is to be found in the fact 

 that the Avicida-contorta beds and the " White Lias " in this county 

 invariably go together ; and allusion has already been made to the 

 continuity of these deposits over large areas in other districts. I 

 believe it is correct to say that there is scarcely an exception luithin 

 the Coal-basin south of Bath (and the same observation might apply 

 heyond it) to the rule that where the Liassic beds are quarried, 

 the '^ White Lias" may be found beneath. Whatever may be the 

 beds above, invariably William Smith's " Sun Bed " (the top bed 

 of the " White Lias ") presents a uniform horizontal platform ; and 

 although these uppermost Eheetic beds are occasionally cut through 

 by the subsequent formation of the valleys of the district in which 

 they occur, their regularity and condition forbid the supposition that 

 they have been subject to any important denuding agencies, which 

 might have been expected had the thinning out, or the absence, of 

 the Liassic rocks above them been due to denudation. 



Within this area organic remains in the " White Lias " are very 

 rare ; and the general character of the deposit is such as we might 



