﻿66 MR. T. F. SIBLY ON THE FAUNAL SUCCESSION IN THE [Feb. I908, 



Province, on the brachiopod- fauna of the Dihunophyllum-Zone in 

 that Province. ^ 



It must be noted that the brachiopod-fauna of D.^ i^ ^^^ Midland 

 area, here contrasted with that of the South-Western Province, 

 occurs in association with the typical D., coral-fauna, in the typical 

 facies of the subzone. The locally-developed ' brachiopod-bed ' - 

 facies of this subzone in the Midland area, in which the coral-fauna 

 is very poor, has no representation in the So nth- Western Province. 



D3 = Subzone of Cyathaxonia rushiana. 



This subzone is unrepresented in the South- Western Province, 

 except by the uppermost beds of the Avonian at Oystermouth 

 (Gower), in which Ample.vi-Zaplirentis and Zaphrentis aff. Ennis- 

 Icilleni are abundant.'^ Since the Ciiathaxonia-swhzowii of the 

 Midland area directly succeeds beds which can be correlated with 

 the Upper Dihunopliyllum-Zone of the South-Western Province, 

 it constitutes a horizon at least as high as the top of the typical 

 Avonian sequence. The occurrence of Productus scahricuhis and 

 Pr. costatus would at first suggest an accurate correlation with 

 Horizon e of the South-Western Province, but it is found that both 

 these species range throughout the greater part of D.„ as well as D^, 

 in the Midland area. In the typical succession of the South-Western 

 Province, Horizon e and the lower part of the Millstone Grit may 

 be taken as representing the Cyathaxonia-suhzone of the Midland 

 sequence. 



(B) Comparison of the Succession in the Midland Area 

 with that in North Wales. 



The faunal succession in the Midland area bears a close resem- 

 blance to that in ]N"orth Wales, recently described by Dr. Wheelton 

 Hind & Mr. J. T. Stobbs,-* and the similarity of these two 

 developments is of considerable interest. Those writers have 

 demonstrated that the basement-conglomerate of the Carboniferous 

 Series in Xorth Wales is of Upper Avonian age, and that no part 

 of the Avonian, lower than the uppermost portion of the Seminula- 

 Zone, is represented in that area. I have found no evidence of any 

 horizon lower than the D'lbunophyllum-ZonQ, in the Midland area ; 

 and the limestones immediately overlying the basement-conglo- 

 merate in certain parts of the Xorth-Wales area, which contain 

 Seminula ficoides and Daviesiella Uangollensis, must be regarded as 

 of lower horizon than any beds seen in the typical section of the 



^ See A. Vaughan, Quart. Journ. Geol. Soc, vol. Ixii (1906) p. 302, footnote. 



^ See above, p. 49. 



^ A. Vaughan, Quart. Journ. Geol. Soc. vol. Ixii (1906) p. 302. 



* ' The Carboniferous Succession below the Coal-Measures in Xortli Shrop- 

 shire, Denbighshire, & Flintshire ' Geol. Mag. n. s. dec. 5, vol. iii (1906) 

 pp. 385-400, 445-59, & 496-507. 



