48 BRITISH AVONIAN CONODONT FAUNAS 
(ii) Farlow (Fig. 53). 
The K Zone samples from Farlow (FAR 4A-—7) yield a fauna broadly similar to that 
of the lower strata of the Avon Gorge, and the North Crop, although there are some 
differences. The lowest beds (FAR 4A) are characterized by the presence of both 
Patrognathus variabilis gen. et sp. nov. and Polygnathus inornatus inornatus, together 
with Clydagnathus gilwernensis gen. et sp. nov., and Polygnathus communis. The 
first and third of these species occur together in the lowest zone of the Avonian (the 
Patrognathus variabilis-Spathognathodus plumulus plumulus Zone) but Polygnathus 
inornatus inornatus is confined to the overlying zone, where it occurs with P. 
inornatus rvostratus subsp. nov., which is found in the immediately overlying sample 
at Farlow (FAR 4), and P. lobatus s.1. which is found in the next overlying sample 
at Farlow (FAR 5). In the Avon Gorge, P. variabilis is associated with Poly- 
gnathus inornatus in this zone. The lowest K Beds of Farlow thus appear younger 
than those of the North Crop or the Avon Gorge. Furthermore, Sample FAR 5 
also contains Spathognathodus cf. robustus, S. crassidentatus, S. elongatus and S. 
tvidentatus, all of which are characteristic of the Spathognathodus cf. robustus— 
Spathognathodus tridentatus Zone of the North Crop and Avon Gorge. It therefore 
appears that the K Zone at Farlow represents a very condensed succession, the 
overlying beds of the K Zone at Farlow yielding an almost identical fauna to that 
of Sample FAR 5. 
The Z Zone strata at Farlow are marked by the appearance of Spathognathodus cf. 
cristulus and Ligonodina beata nom. nov. in the lowest beds (ORZ 1) and Spathog- 
nathodus costatus costatus, and Clydagnathus darensts gen. et. sp. nov. in the overlying 
beds (ORZ 2). These species are characteristic of the Spathognathodus costatus 
costatus-Gnathodus delicatus Zone, as is Clydagnathus unicornis gen. et sp. nov., 
which occurs in the overlying beds (ORZ 3). A single specimen of Gnathodus 
antetexanus in Sample ORZ A3, represents an anomalous faunal association, since 
its first appearance in the Avon Gorge is in beds of Zz age. 
(iii) Yorkshire (Fig. 54). 
A reconnaissance sampling programme of the Yoredale succession has yielded 
abundant and well preserved conodont faunas characteristic of the higher Avonian 
zones of the South Western Province. Although we have dissolved 7 kilogrammes 
of the Hawes and Gayle Limestones, the beds have yielded no diagnostic conodonts. 
The Hardraw Scar and Simonstone Limestones contain Gnathodus mononodosus sp. 
nov. and G. homopunctatus and thus fall within the G. mononodosus Assemblage Zone. 
The fauna of the overlying Middle Limestone is marked by the first appearance of 
Gnathodus girtyi collinsoni subsp. nov., and the Five Yard Limestone is characterized 
by the first appearance of G. girtyi turritus. These limestones therefore represent 
the G. girtyi collinsoni Zone. Although Varker (1967) has suggested that species of 
the genus Apatognathus may provide a useful basis for zonation and correlation in 
the Yoredales, we have found the genus to be rare, rather than common, as he 
claims, and we do not consider it useful in correlation. 
a LL 
