BRITISH AVONIAN CONODONT FAUNAS 65 
Formations of North America. Pseudopolygnathus dentilineatus of Conil e¢ al. in 
Tngp is synonymous with Pseudopolygnathus multistriatus of Mehl & Thomas in the 
U_S-A. 
This would also suggest that the Tournaisian—Viséan boundary in the cephalopod 
facies of Germany should not be drawn as at present at the top of Cu II «, but higher 
in the succession at the top of Cu II. 
There are, however, two complications. Firstly, the type fossil of the Cu II « 
horizon, Pericyclus princeps, although never recorded from Germany, is recorded from 
the Ing, horizon of Belgium. Secondly, Pseudopolygnathus triangulus inaequalis is 
confined to Tng, in the Franco-Belgian Province and to the middle of the Cu I in 
Germany. This might imply that the German Upper Cu I and Cu II « horizons are 
equivalent in terms of the Franco-Belgian Tournaisian to the bedding plane boundary 
of Tn3.-Tngp,, but we have some reservations about the general applicability of the 
subspecies of Ps. tviangulus established by Voges. 
In Britain none of the genera Scaliognathus, Staurognathus, Doliognathus, or 
Bactrognathus have been found in the Avonian, although Matthews (1961) did record 
Scaliognathus anchoralis, Hindeodella segaformis and Doliognathus latus from the 
Lower Carboniferous in East Cornwall. Thus these fossils, characteristic of the 
anchoralis Zone in Germany were present in the British Lower Carboniferous seas. 
One possible explanation of their non-appearance in the Avonian is that the 
anchoralis Zone of Germany is represented in the Avonian by the Zz Fish Bed, which 
would thus represent a considerable non-sequence. 
Alternatively Scaliognathus anchoralis and its typical zonal associates may be 
limited in their distribution, either by facies or geography. This is supported by the 
fact that in North America, from which it was first described, S. anchoralis is known 
only from Branson & Mehl’s type specimen, and further intensive sampling of the 
type locality by Dr. C. W. Collinson has failed to produce even one additional 
specimen (personal communication). It does not seem to be present in Australia, 
although it is abundant in Germany, France, Belgium, Spain and North Africa. 
Some of the typical associated genera display similar anomalies in distribution. 
Doliognathus is abundant in some sections in Germany, but absent in others, even 
though its zonal associates are present in both. It may be that this group of rather 
bizarre genera are components of one or more natural conodont assemblages of 
limited tolerance. If this alternative explanation is correct, the anchoralis Zone of 
Germany may be represented not by a hiatus but by a succession with a different 
fauna in the Avonian. The exact limits of correlation are difficult to determine, 
but would lie within the Upper Z to Lower C Zones. 
It seems possible, however, that the anchoralis horizon is equivalent to the lower 
part of the Canimia Dolomite of the Avon Gorge, which has yielded no conodont 
faunas. 
VI. SYSTEMATIC PALAEONTOLOGY 
The following section contains descriptions of the species recorded in the present 
study. The ranges recorded in the descriptions refer to sample numbers that are 
listed on p. 292. 
