Vol. 67.] THE CARBONIFEROUS SUCCESSION IN GOWER. 567 



Figs. 2 a & 2 b. Productus longispiuus Sow., var. (p. 560). D 2-a of Oyster- 

 mouth Quarry. Fig. 2 a, cast of interior of brachial valve, X 1'5 ; 

 Fig. 2 b, pedicle-valve (showing wing), x 1*6. 



Figs. 3 a & 3 6. Chonetes sp. (p. 5(>1), natural size. Fig. 3 a, cast of pedicle- 

 valve ; D 2 ^ 3 (top), Bishopston. Fig. 3 b, pedicle-valve from D 2 _ 3 

 of Oystermouth Quarry. 



Fig. 4. ' Orthotetes' cf. crenistria (Phill.) (p. 561). Brachial valve and area, 

 natural size. D 2 _ 3 of Oystermouth Quarry. [The specimen is 

 crushed, and does not show the strong convexity of the valve.] 



Figs. 5 a & bb. Spirifer bisulcatus, var. oystermouthensis nov. (p. 562). 

 Fig. 5 a, pedicle-valve, natural size. D ~ 3 of Oystermouth. Quarry. 

 Fig. 5 b, portion of a brachial vnive, enlarged to show ornament. 

 Same locality. 



Fig. 5c (for comparison). Spirifer calcaratus M'Coy (p. 562), natural size; 

 a pedicle-valve from D 2 _ 3 of LolJey Scar Quarry, near Pateley Bridge 

 (Yorkshire). 



Fig. 6. Spirifer nr. increbescens Hall (p. 562), natural size ; a brachial valve 

 from D 2 - 3 of Oystermouth Quarry. 



Fig. 7. Spirifer wickensis, sp. nov. (p. 563), natural size, a pedicle-valve from 

 D . 3 of Oystermouth Quarry. 



Fig. 8 a. Athyris ( Cliothyris) globularis(Yh\\\.) (p. 564), a pedicle-valve, X 1*5. 

 D 2 . 3 of Oystermouth Quarry. 



Fig. 8 b (for comparison). Athyris (Cliothyris) roissyi of the ' Bristol Paper.' 

 Beak and brachial valve. X 1'6 (p. 564). Km (' Modiola phase') 

 of the Avon Section. 



Discussion. 



Dr. A. Strahan observed that this region was one which called 

 especially for combined stratigraphical and palseontological work. 

 The Carboniferous Limestone Series presented a succession of stages 

 in development. The fullest development was exhibited in the 

 southernmost occurrences, as regarded both the sequence and the 

 thickness of zones. A second stage, showing an incomplete sequence 

 and considerable attenuation, with indications of near-shore origin, 

 was presented along parts of the margin of the coalfield. Lastly, 

 in the northernmost occurrences, near Abergavenny and at Pen- 

 cerig-calch, the series dwindled away to 100 feet or less, while in 

 Pembrokeshire it was wholly overstepped. The inference followed 

 that the coast-line ran through Pembrokeshire, and not far north of 

 Abergavenny. Traverses made at right angles to the coast-line, 

 and comparisons of these various stages of development, could not 

 fail to yield results of the greatest interest. The only other district 

 where such a traverse was possible, lay on the northern side of this 

 same Carboniferous land-area, where the Limestone Series could be 

 followed continuously through Denbighshire to its disappearance 

 in Shropshire. That the radiolarian cherts were of shallow- water 

 origin seemed obvious, nor, so far as he was aware, was there 

 evidence of deep water in any part of the Limestone Series : 

 sedimentation or formation of organic deposits seemed to have 

 kept pace with subsidence so nearly that the water was generally 

 shallow. But he was unable to follow the Authors in their iden- 

 tification of lagoon-phases. He enquired whether further evidence 

 had been obtained for identifying and defining the Posidonomya 

 Zone. The change of fauna at the base of the radiolarian cherts 



