74 THE RH^ETIC OP WEST, MID, AND EAST SOMERSET. [Feb. I9II, 



favour of one which was wholly indefinite, as the base of the 

 Rhsetic group. 



The President (Prof. Watts) expressed his sense of the importance 

 of the Author's work and of the interest of the non-sequences 

 revealed by a close study of the Jurassic and Rhaetic zones. In the 

 matter of mapping, he thought that it would always be necessary 

 to carry on the practice of field-mapping by means of physical 

 characters, the true position of the beds being checked by palaeonto- 

 logical evidence. 



The Author, in reply, said that more field-work was necessary 

 before the precise horizon at which insect-remains occurred could 

 be indicated. Referring to Mr. Stanley's remarks, he was not 

 aware of any facts to suggest that there was a non-sequence 

 between the Red Marls and the Tea-green Marls in Warwickshire ; 

 but he did hold that there was a gap between the latter and the 

 Black Shales — he thought that the Sully Beds and the bottom 

 portion of the Black-Shale subdivision were wanting. 



With regard to Aust Cliff, the Author held that the Sully Beds 

 and practically the whole of the infra-Bone-Bed deposits were 

 absent, and those who knew from personal investigation the 

 ordinary phenomena associated with non-sequences would appreciate 

 the significance of rolled masses of Tea-green Marl embedded in 

 the Bone-Bed there. 



In reply to a question put by Mr. Monckton, the Author 

 remarked that most Rhaetic field- geologists felt that the White 

 Lias proper ought to be grouped with the Rhaetic ; and yet, at 

 the same time, they realized that it and the underlying West bury 

 Beds and overlying Watchet Beds were very distinct from the 

 Pteria-contorta Black Shales. Hence the suggested dual division 

 of the Rhaetic Series into Rhaetian and Somersetian : a division 

 supported both upon lithological and upon palaeozoological grounds. 



In reply to Dr. Marr, the Author thought that if he had altered 

 the term 'Rhaetic' to ' Rhaetian,' it would have complicated the 

 nomenclature. The term « Rhaetic,' according to the proposed 

 classification, would be available for colloquial purposes in the same 

 way as the terms ' Inferior Oolite ' and ' Lias ' : otherwise, such 

 well-known terms as 'Lias' would have to be modified. 'Rhaetian' 

 and ' Somersetian ' came into line with such terms as 'Hettangian,' 

 ' Aalenian/ ' Bajocian,' etc. 



In reply to Dr. Strahan, the Author exhibited a specimen of 

 Pteria contorta from a horizon well down in the Sully Beds at 

 Lilstock in West Somerset, and specimens of this and other fossils 

 from the equivalent beds at Cadoxton and Sully in Glamorgan. 

 Prof. Boyd Dawkins had also recorded characteristic Rhaetic fossils 

 from the Sully Beds, or, as they were called at the time, the ' Grey 

 Marls' (pa?*s), of Watchet. He agreed with Dr. Strahan and the 

 President that, for mapping purposes, the Sully Beds must be 

 associated with the Tea-green Marls (Keuper). The occurrence in 

 them of Rhsetic fossils was of purely scientific interest. 



