480 ME. E. E. L. DIXON AND DR. A. VAUGHAN ON [NOV. I9II, 



Dr. "W. B. Gubbin l ; and it Avas desired that our knowledge 

 should be extended to the whole development, as also to the 

 relationship of the zones that are based on brachiopods and corals 2 

 with the representative of the Pendleside Series which had been 

 recognized in Grower by Dr. Wheelton Hind. 3 For in Gower 

 alone of the whole province was such a representative known. 4 

 Between 1899 and 1902 the area had been mapped by the officers 

 of H.M. Geological Survey, Dr. A. Strahan, Mr. B. H. Tiddeman, 

 and Mr. B. S. ~N. Wilkinson, and our work was greatly facilitated 

 by the knowledge then obtained, which was generously placed at 

 our disposal and has since (in 1907) been published in the official 

 maps and memoirs. 5 



Our joint field-work, the examination of the Mumbles-Bishopston 

 ground and the southern coast, was carried out in 1905, and in the 

 following year one of us (E. E. L. D.) extended the work into the 

 north-western part of the area in connexion with the Geological 

 Survey ; a summary of the information then obtained has since 

 been published. 6 



II. LlTHOLOGICAL CHARACTERS OE THE ZONES [E. E. L. D.]. 



The Avonian rocks of Gower (see map, fig. 2, p. 479, based on the 

 Geological Survey maps previously mentioned) form part of the 

 southern margin, the 'South Crop,' of the South Wales coal-basin. 

 They present several outcrops, ranging west-north-west on the 

 whole, as they have shared in the powerful Armorican folding 

 about axes having that direction, which is the dominant structural 

 feature of the whole area. The folds are chiefly elongated 

 periclines, and the several Avonian outcrops along the limbs are 

 continuous one with the other. 



These outcrops represent the deposits of an area of the Avonian 

 sea which extended for some distance both eastwards and west- 

 wards (that is, parallel to the coast-line lying at no great distance to 

 the north), and northwards and southwards ; and the bearing of this 

 fact on the development in different districts will be pointed out. 



In the east, between Mumbles and Cefn-y-Bryn, only one major 

 fold — the Cefn-y-Bryn pericline — appears above the sea, and the 

 Lower Carboniferous rocks which form its eastward-pitching ' nose/ 

 though presenting several outcrops on account of minor folding, 

 may be grouped together as the Eastern District. But iu the west, 

 rocks of the same age occur over a wider extent of country. At 



1 Proc. Bristol Nat. Soc. ser. 4, vol. i (1905) p. 42. 



2 A. Vaughan, Q. J. G. S. vol. lxi (1905) p. 181. 



3 Geol. Mag. 1902, p. 485 ; ibid. 1904, pp. 402, 585-87. 



4 Recently, Dr. Hind has correlated some beds at Tenby with the Pendleside 

 Series, Proc. Geol. Assoc, vol. xxi (1909) p. 179. 



5 The Swansea sheet (N. S. 1-inch map 247) and ' The Country around 

 Swansea ' 1907 ; the Worms-Head sheet (N. S. 1-inch map 246) and • West 

 Gower & the Country around Pembrey' 1907. These memoirs will be referred 

 to as the ' Swansea Memoir ' and the ' West Gower Memoir ' respectively. 



6 West Gower Memoir, pp. 14-17. 



