ON LOWER CARBONIFEROUS ZONAL NOMENCLATURE. 263 
Sus-Report I. 
(E. E.L.D.) 
I do not think it desirable to tie our hands by adhesion to the use of the term 
Viséan. The sequence at Visé is abnormal and unlike that found anywhere else in 
Belgium or in Great Britain. 
It would probably be generally agreed that were it not that the term Viséan is 
already in the field, the best horizon at which to separate the Yoredalian would be the 
base of D,. This should be done, though the use of Viséan for the beds below then 
becomes impossible, as the Viséan includes D, if it includes anything. It is agreed, too, 
that Continental names should be used in the exact sense in which they are used 
abroad. The use of Tournaisian would already appear to be inadvisable, as the Belgian 
Tournaisian does not include our Cleistopora Zone (K). Consequently, British terms 
should be used for all the Lower Carboniferous, as for the Upper (e.g. Yorkian instead 
of Kidston’s Westphalian). 
Although the separation of a Yoredalian is useful, the Avonian should be divided 
primarily into two, not three, series, the upper to include the Yoredalian and the beds 
below down to the base of C,. The Yoredalian is not sufficiently marked off, palaeon- 
tologically, lithologically, or stratigraphically, from the beds below to warrant its 
separation as a major division. This is shown by the uncertainty as to the best 
horizon for its base. To the horizons mentioned might well be added the base of 
the Great or Main Limestone, adopted by Vaughan and mapped practically wherever 
the Yoredales are known. 
The Avonian would then consist of an upper series, comprising the Yoredalian 
above and an equivalent of the Viséan, less D,, below, and a lower series (=Tour- 
naisian+K). 
The Yoredalian, as I conceive it, cannot overlap the Lancastrian. The base of 
the Lancastrian is defined by Bisat at the entry of a new goniatite-fauna of Upper 
Carboniferous facies. The Yoredalian, therefore, as a time-division of the Lower 
Carboniferous automatically comes to an end at this level, in accordance with the 
generally-received rule that a younger flora or fauna determines a younger formation. 
This delimitation is supported by the evidence, found in places, of unconformity 
at the base of the Lancastrian. Whether the Yoredale facies of deposition (as 
against the Yoredale period) has persisted into Lancastrian time in Scotland remains 
to be proved. Should the proof be forthcoming, the demarcation must be reconsidered, 
as the deposits of Yoredale facies of Scotland also are separated in places from the beds 
above by an unconformity. 
Sus-Report II. 
(W.S. B., W.B.W., J. W.S., L.H.T., D.P.) 
' The undersigned, having freely discussed among ourselves and with the Secretary, 
the matters dealt with in this Report, and having, in order to obtain general agreement, 
accepted much that appeared to us undesirable, have found it at length necessary te 
take exception to the character of the recommendations made. 
The Report deals almost exclusively with the coral-brachiopod faunal phase ot 
the Carboniferous, and even after extensive modifications still clearly seeks to establish 
this phase as the standard by which the time-divisions of the period are to be defined, 
and to which the other phases, such as the Culm or Goniatite phase, are to be referred. 
This is apparent in the failure to obtain agreement in the use of the zone ‘ P’ in the 
significance originally attached to it by Vaughan, and recently more accurately 
delimited by one of us in terms of a clear-cut and well-defined fauna. The main reason 
given for its non-recognition by the Committee is that it has been inaccurately and 
wrongly used by a number of workers on the coral-brachiopod faunas. ‘P’ is, however, 
essentially a Culm zone, and the workers on the Culm faunas naturally claim the right 
to use it, and even re-define it, if they think the procedure is sound. The use and re- 
definition of it is as justifiable as the use and re-definition of ‘D ’ recommended in 
the Report, to which we have agreed as a time-division of the coral-brachiopod phase. 
It appears to us to be more capable of accurate definition and to be traceable over a 
wider area than the zone ‘D’ and its subdivisions, and much more so than the 
succeeding coral-brachiopod zone ‘ O,’ suggested by the Committee and accepted by 
us as a subdivision of that phase in the North-West Province. 
It is true that in the body of the Report the necessity for ‘ two parallel and con- 
temporaneous sets of zones, the one set based on the standard limestone fauna, and 
