Vol. 67.] THE CARBONIFEROUS SUCCESSION IN GOWER. 503 



present, are rare ; their place is, apparently, taken by limestones 

 that are rather less fine-grained and contain an abundance of 

 CalcisjjhcFra (?) and foraminifera. These rocks and the ' pisolites ' 

 are interbedded with oolite like that of Group 2 below, their lower 

 limit being unknown but probably quite indefinite. Upwards the 

 change to Zone D with its characteristic fauna and sediments is 

 comparatively rapid, the highest bed definitely assignable to S 2 being- 

 separated from the lowest undoubted D limestone — the oolite 

 described on p. 504 — by 24 feet of limestones of less determinate 

 relations. 



2. Chiefly light-grey, thickly-bedded oolites, many sparingly 

 fossiliferous ; some fine-grained limestones, composed of current- 

 bedded organic detritus. At intervals occur dark, finely-crystalline 

 dolomites, up to several feet thick, which, though in some cases 

 markedly impersistent along the bedding, as already described by 

 Dr. Strahan (West Gower Memoir, p. 13), are inferred, from their 

 microscopic characters, 1 to owe their alteration to the influence of 

 the Carboniferous sea. Near the base of the group the limestones 

 contain sporadic, light-grey sponge-cherts, of concentric, alternately 

 siliceous and calcareous zones. Thickness, including the Modiola 

 phase above, between 820 and 870 feet. 



1. Gasteropod-limestones, 2 dark, highly bituminous, and well- 

 bedded ; many of the gasteropods selectively dolomitized in the 

 way described on p. 484 ; cherts and beekitized fossils. Thickness 

 = 120 feet. 



S x :- 



2. Gasteropod-limestones, dark and continuous with those above, 

 but on the whole more thinly-bedded, and separated from one 

 another by soft shaly partings ; highly fossiliferous (p. 547) ; 

 beekite in fossils in the upper beds : some beds more or less 

 dolomitized. Thickness = 105 feet. 



1. Limestones, similar to the underlying C 2 limestones ; less 

 fossiliferous than the beds above ; little dolomite and no chert or 

 shale. Thickness =115 feet. 



The whole zone is exposed in the cliffs and shore near Port- 

 Eynon Point, from the bluffs at the cliff-foot, west of Overton 

 Mere, 3 where S t is finely displayed, eastwards to Sedgers Bank, 

 where D comes in. S x and S 2 enter largely into the cliffs on the 

 west, also, of Overton Mere, as far as Mewslade Bay. 



i Similar to those of contemporaneous dolomites described in the Swansea 

 Memoir, pp. 16-20 & pi. i, fig. 4. 



2 Included by Dr. Gubbin in S x ; the absence of Caninia bristolensis Vaughan 

 has led to my placing this group in S 2 . 



3 Details from this locality, especially of the gasteropod-beds, are recorded 

 by Dr. Gubbin (Proc. Bristol Nat. Soc. ser. 4, vol. i, 1905, pp. 44-50), who has, 

 however, greatly underestimated the thickness of S 2 ; the ' black calcareous 

 sandstone' to which he refers on p. 47 is the dolomite in Group 2 of S 2 , 

 mentioned above. 



