part 1J STRATIGRAPHY OF THE SHALES-WITH-' BEEF.' 51 



Since 1914, a great deal of material has been collected ; and it 

 has been found desirable to subdivide the horizons still further, in 

 order to arrive at a more exact faunal sequence. Moreover, the 

 cliff-section immediately west of Charmouth has been correlated 

 with the sequence on the reefs. Of course, it is not to be supposed 

 that the minute subdivisions will be found farther along the cliff, 

 or even that the prominent beds at the Charmouth end of the 

 section will necessarily persist as far as Lyme, or to the mile west 

 of Lyme where the Shales-with-Beef occur ; the fauna alone will 

 correlate horizon with horizon along the cliff-section, and at isolated 

 exposures inland. But, until the faunal sequence is determined, 

 this correlation cannot be made ; and, in order to find the faunal 

 sequence, it is necessary to subdivide a standard section minutely. 

 The accessible western part of the outcrop has therefore been 

 selected for the purpose, and it is hoped that the reason given 

 explains and excuses the subdivision of some 70 feet of shales into 

 more than a hundred horizons. 



In 1917, Mr. S. S. Buckman read a paper before this Society 

 on the British Lias, in which he drew attention to the phenomenon 

 called by him faunal repetition. 1 In the same paper, Mr. J. W. 

 Tutcher 3 gave an ammonite sequence in the Bath-Radstock 

 district, in Lias corresponding to that here described. His sequence, 

 from below upwards, was A. scipionianus, A. sauzeamis, A. turneri 

 [Jl. birchi], differing from Buckman's sequence 3 in the last two 

 terms ; for Mr. Buckman puts A. turneri above M. birchi. Thanks 

 to the researches of Dr. L. F. Spath, who has kindly examined 

 my ammonite material from these beds, and contributes a pahe- 

 ontological part to this paper, it has been possible generally to 

 correlate the horizons of the Shales-with-Beef with the three top- 

 most horizons in the Bath-Radstock area just mentioned. The 

 correlation is as follows : — Horizon of A. sauzeanus = below (53) 

 Table Ledge to 70 e; M. birchi = 7 4g-7 5; and A. turneri=76sL. 

 Thus the beds from 70 f to 71 f are not represented in the Bath- 

 Radstock area. It is true that in Dorset there is a faunal repeti- 

 tion 4 of Arietites : thus, there is a lower Arietite fauna in 73 & 

 74 d, below the M. birchi horizon ; and an almost exactly parallel 

 Arietite fauna, including the true A. turneri, in 76a & 76b, above 

 the M. birchi horizon. But the specimens of A. turneri on which 

 Mr. Tutcher founded his sequence, and on the exact field-relation 



1 Q. J. G. S. vol. Ixxiii (1917-18) p. 267. 



2 In S. S. Buckman, op. cit. p. 279. Mr. Tutcher does not add M. birchi to 

 -fche top of his sequence. It is evident, however, that he did not suppose that 

 M. birchi came between his A. sauzeanum and A. turneri, but that it was 

 later than A. turneri. 



' A Op. cit. p. 277. 



4 In these beds faunal repetition is also seen in the Schlotheimia [Sulci- 

 ferites Spath] fauna associated with the lower Arietites ; in the Coroniceras- 

 like forms \_Paramioceras Spath] in the P.-alcinoe bed ; in the reappearance 

 of Agassiceras above Table Ledge (53), and of Arnioceras above the Broohi 

 Bed. 



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