﻿80 ME. T. F. SIBLY OX THE FAUXAL StJCCESSIOX IX THE [Feb. I908, 



EXPLANATION OF PLATE I. 

 AvoniaB Corals and Bracliiopods from the Midland Area. 



[All the figured specimens are preserved in the Author's collection ; and 

 they are shown of the natural size, except where otherwise stated.] 



Fig. 1. Bibuuaphi/llum derbiense, sp.nov. (p. To). Horizontal section. D, sub- 

 zone ; Monsal Dale (Derbyshire). 



2. Bihunophyllum laatlocTcenae, sp. nov. (p. 74). Horizontal section. 



D2 subzone ; near Wensley (Derbyshire). 



3. Koninck&phylhim jproprium, sp. nov. (p. 70). Horizontal section \ 



X 1'36. Do subzone ; near Wensley (Derbyshire). 



4. Clhiaphyllum aff. M' Coyanum. Thomson (p. 73). Horizontal section. 



D., subzone ; Darleybridge (Derbyshire). 



5. Lonsdalia duplicata (Mart.) (p. 72). Horizontal section. D.., subzone \. 



Monsal Dale (Derbyshire). 

 Figs. 6 a & 6 Z>. Productus setosus, Pliil., var. tissingtonensis. nov. (p. 77). 

 D3 sabzone ; Tissington (Derbyshire). 

 Fig. Ota = Convex valve ; fig. (Mj = Another specimen : view of frontal 

 portion of a convex valve, to show the nature of the 

 ribbing. (Mesial fold imperfectly preserved) ; X 1"1. 

 Figs. 7 « & 7 h. Chonetes compressa, nom. nov. (p. 78). D.^ sabzone, Wirksworth 

 (Derbyshire). 

 Fig. 1 a = Pedicle-valve (imperfect) ; fig. 1 h = Another specimen, 

 brachial valve. 



Discussiox. 



Dr. "Wheeltox Hixd congratulated the Author on his detailed and 

 accurate work. He felt most pleased that the Author's researches 

 had completely vindicated the speaker's previous publications on the 

 area ia question and on jS'orth Wales. He had no adverse criticism 

 to make, but would discuss the important bearing of details. As 

 to North Wales, at the top of D^ lithological structure varied 

 considerably on the same horizon, and it was impossible to map 

 by lithology. The cherts might replace any part of the series Dg, 

 and were evidently not original depositions. The true cherts were 

 chiefly found in the upper part of the Dihuno])hyllum-ZonQ, but 

 occasionally some of the Pendleside Limestones were very cherty. 



The very fossiliferous deposits of Park Hill, Wetton, etc., in the 

 Lonsdalia-Zone were correctly referred to that horizon. The speaker 

 had always regarded them as shell-banks, and to that extent original. 

 All kinds of fossils, which must have inhabited different bathy- 

 metrical zones, with others which undoubtedly lived in the shell- 

 bank, were jumbled up together without any definite stratification. 

 In connexion with these beds, the speaker alluded to beds of 

 rolled and water-worn shells at Castleton and other places outside 

 the area now dealt with. 



There could be no doubt that the succession in North Staffordshire 

 was similar to that in North Wales, and that both areas belonged 

 to the same province. 



The pre- Carboniferous physiography of the area was an interesting 

 question, for in Derbyshire the DibunopJiyllum-ZoTiQ, the Pendleside 



