216 BRITISH AVONIAN CONODONT FAUNAS 
P. primus developed from P. dentilineatus in the Avonian. Three morphological 
variations of P. primus have been observed : those with a wing-like expansion at 
the anterior (Pl. 6, fig. 10), those with a considerably larger right side to the platform 
(Pl. 6, fig. 7) and those where there is a distinct trough on the left side of the anterior 
part of the platform (PI. 6, figs. 11, 12). This latter variation closely resembles P. 
multistriatus and becomes the dominant form of P. primus in the middle part of the 
Z Zone. 
Pseudopolygnathus triangulus cf. pinnatus Voges 
Plate 30, fig. 19 
1959 Pseudopolygnathus triangula triangula Voges : 304, 305, Pl. 35, figs. 7-13, p. 297, text-fig. 
5 IV. 
1963 Pseudopolygnathus triangula subsp. indet Voges ; Ziegler : Pl. 1, figs. 1, 2. 
1963 Pseudopolygnathus triangula triangula Voges ; Ziegler: Pl. 1, figs. 3, 4. 
MATERIAL. 3 specimens : figured, X 502. 
RANGE. Avon Gorge C 7. 
DEscrRIPTION. This species is characterized by having a platform with a triangular 
outline. It is straight and wide at the anterior edge of the platform. The platform 
in oral view is widest slightly anterior to its mid-length. It tapers gradually to the 
posterior, having straight margins and a triangular posterior outline. Anterior to 
the mid-length, the margin of the platform is gently curved and it tapers suddenly 
to the anterior. The anterior blade is broken. The platform is one and a half times 
as long as wide and has a straight axis. The oral surface of the platform is flat to 
slightly concave and is ornamented by a number of ridges normal to the margin, 
which are confined to the outer half of the platform and do not reach the carina. 
The central carina is strongly developed and has knob-like projections on its upper 
surface. 
The aboral surface is flat and wide. The margins of the outer position are slightly 
upturned. A strong keel runs the length of the unit, interrupted by the small 
anteriorly situated pit of the basal cavity. 
REMARKS. The specimens found in the present study most closely resemble 
Pseudopolygnathus triangula subsp. indet Ziegler (1963), but the anterior edge of the 
platform is neither as straight nor as wide as it is in the type specimen (Voges 1959). 
The present specimens have a more rounded anterior extremity. 
Pseudopolygnathus vogesi sp. nov. 
Plate 5, figs. Ia—c, 3a—c, 5a-8 
?1956 Pseudopolygnathus striata Mehl & Thomas ; Bischoff & Ziegler : 164, Pl. 11, fig. 20. 
21957 Pseudopolygnathus dentilineata E. R. Branson ; Bischoff: 50, 51, Pl. 4, figs. 30, 31, 
32 only. (non Pl. 4, fig. 29 = Pseudopolygnathus primus). 
?1959 Pseudopolygnathus dentilineata E. R. Branson ; Voges: 297, text-fig. 5, fig. II, Pl. 34, 
figs. 49, 50. 
?1964 Pseudopolygnathus sp. Bouckaert & Ziegler : 27, Pl. 4, fig. 12. 
