﻿262 DR. A. VATTGHAN ON THE PALiEONTOLOGICAL [May 1905, 



section, is, from a palseontological point of view, indefensible, for 

 the following reasons : — 



(1) At the point where the shales start the Dibunop hyllum-i auna is already 

 well established, and the limestone-bands included in the shales contain a 

 fauna which is indistinguishable from that in the topmost beds of the under- 

 lying massive Limestone-Series. 



(2) In many localities the whole series is composed of massive limestones 

 (for example, Tenby, the Mendips). 



The essential fact in the Dibunophyllum-fsicies is the dominance 

 of the Clisiophyllid-family, and the ultimate impression of a 

 Clisiophyllidan character upon the whole of the coral-fauna. 



The #</> and Lonsdalia-Subzones. 



The 0<p-subzone is characterized by Clisiophyllids belonging to 

 several sections ; the subzonal index itself represents a generalized 

 division of the gens of Dibunophyllum turbinatum. 



This subzone contains the maximum of Cyathophyllum MurcMsoni 

 in its type-form. In this form the Zaphrentid characters, which 

 were so noticeable a feature of the early Cyathophylla {Cyatho- 

 phyllum (p, C 2 and S 2 ), have, in the Dibunopliyllum-Zone, become 

 almost entirely lost. 



In the Lonsd a Z^tf-Subzone the acme of the Clisiophyllidan 

 phase of structure is reached. 



Lithostrotion which, up to this subzone, forms the staple element 

 in the Yisean coral-fauna, gradually adopts the Clisiophyllidan 

 character and becomes merged in Lonsdalia. Cyathophylla of the 

 type of Cyathophyllum MurcMsoni, yielding to the same tendency, 

 evolve forms of the type of C. regium. 



The gens of Dibunophyllum turbinatum reaches its maximum 

 specialization in the group represented by Dibunophyllum xp. 



Horizon e. 



This horizon is well characterized by a group of scabriculate and 

 spinose Producti (Pn cf. costatus and Pr. cf. semireticulatus), and 

 contains the remnants of a Carboniferous-Limestone facies in the 

 presence of Orthotetes crenistria and Productus Cora (mnt.). 



The horizon being represented in widely-distant areas, and 

 being the highest horizon at which a Carboniferous-Limestone fauna 

 is found, forms a valuable datum-line for fixing the uppermost limit 

 of the Carboniferous Limestone. 



The ' Millstone-Grit/ 



The base of this lithological division is, as I have shown, a 

 variable horizon. At Kidwelly it occurs immediately above 

 Horizon e ; at Bristol it occurs immediately above D 2 , so that 

 Horizon e is included in the ' Millstone-Grit' ; at Mitcheldean it 



