﻿472 DR. C. A. MATLEY AN^D DE. k. VAUGHAN [Aug. I908, 



Fig. 8. Martinia glabra (Martin), old-age mutation (p. 468). Peclicle-valve ; 

 natui'al size, L8jp, Upper Fosidonomya-'Bed^. 

 9. Sjpiriferina f;?sc?^/2JZ'rt (Phillips), large form (p. 468) ; natural size. Frag- 

 ment of impression, to show ornarnent. L 8p, Upper Fosidoncnnya- 

 Beds. 

 10. Acti/wconchus (?) sp. (p. 470). Brachial valve ; X 1*2. L 8^, Upper 

 Posidonomya-Beds. 



Discussion. 



Dr. Wheelton Hind most heartily congratulated the Authors 

 on the final result of their work on the Eush sequence. He felt 

 that he was in entire agreement with their results. He was much 

 interested in the identification of an upper and a lower Posidonomya- 

 Zone. When writing the description of Posidonomya Beclieri for the 

 monograph on British Carboniferous Lamellibranchs, he had with 

 some temerity figured specimens from the limestone of Castleton, 

 in which Productus striatus and Pr. jyroboscideus were associated 

 with it, and the species was known to occur in the shales con- 

 nected with the Hardraw-Scar Limestone of Wensleydale. The 

 Ux^per Posidonomya-Beds were the most important, because in them 

 the zone-fossil was associated with a new fauna, characterized by 

 various goniatites and Pterinopecten papyraceus. The sequence at 

 Rush was homotaxial with that of the Carboniferous rocks in the 

 Midland area and in the Isle of Man. 



With regard to Productus humerosus, this fossil occurred in the 

 uppermost beds of the Dihunophyllum-ZonQ at Swinden Moor in 

 Yorkshire, where it was associated with Zaphrentids of a high 

 Dihunopliyllwn-fsicies. The distribution oi MicheUnia was of interest : 

 a megastoma-\\kQ form was very common in the Isle of Man with a 

 DibunojjliyUnm-fsiUiia., and it was also found at the base of the 

 Arnside Series. MicJielinia tenuisepta was very common in the 

 Cyatha.vonia-BediS of Bradbourne (Derbyshire). Zaphrentid corals 

 were a marked feature in the Upper Dibunop)hyllum-Zone of 

 Derbyshire, Yorkshire, and the Isle of Man. Therefore the speaker 

 thought that the later correlation of Dr. Yaughan was the more 

 probable. 



The speaker remembered with great pleasure having been taken 

 over the section by Dr. Matley some few years ago, before the 

 publication of Dr. Yaughan's enlightening work, and having re- 

 cognized that, at any rate, the Posidonomya-Beds gave an important 

 horizon for correlation with other areas. 



Mr. E. E. L. Dixon, in congratulating the Authors on an 

 important piece of work, observed that the sequence at the top of 

 the Avonian at Eush was of great interest, and he only regretted 

 that it had not been carried oat before the recent work in Flint- 

 shire, as it would have shown that the diff'erence between some of 

 the conclusions as regarded the correlation arrived at in that district, 

 and those of previous observers, was not so great as the previous 

 speaker had supposed. 



Mr. G. W. Lamplugh complimented the Authors on the excel- 

 lence of their work upon this important and difficult section. Their 

 results had simplified the interpretation of the succession and would 



