210 BRITISH AVONIAN CONODONT FAUNAS 
margin to the carina. The inner side of the platform is ornamented by up to eleven 
ridges, the posterior two being nodose at the margin ; the ridges in the posterior half 
of the inner platform extend to the carina from the margin. Those of the anterior 
half do not reach the carina and a trough is present, which is open to the anterior. 
The anterior edge of the inner part of the platform is lower on the carina than is the 
anterior edge of the outer part of the platform, which is at the same level as the 
carina. The 4 posterior denticles of the carina are nodose, but the remainder of the 
carina is composed of fused denticles. 
The basal cavity is asymmetrical, pointed posteriorly and rounded anteriorly. 
Both the inner and outer margins of the basal cavity are expanded laterally in the 
anterior half. The anterior blade js of unknown form. 
Remarks. Pseudopolygnathus expansus sp. nov. is closely related to Pseudopoly- 
gnathus vogesi sp. nov. and transitional specimens have been found (PI. 5, fig. 6-7), but 
is distinguished from it by the expanded anterior portion of the outer side of the 
platform. In this respect it resembles P. primus and is interpreted here as a homoeo- 
morph of the latter species. 
Pseudopolygnathus cf. fusiformis Branson & Mehl 
Plate 6, fig. 1 
1934 Pseudopolygnathus fusiformis Branson & Mehl : 298, Pl. 23, figs. 1-3. 
MATERIAL. I specimen: figured, X 552. 
RANGE. Avon Gorge, C 14. 
Description. A narrow platform is developed on either side of the strongly 
denticulate carina. The platform is widest anteriorly and tapers uniformly to the 
pointed posterior. In lateral view the platform is arched. The margins of the 
platform are notched and edged by 5 or 6 nodes. The blade is almost: as long as the 
platform, and contains 7 denticles, which are fused with the high denticles of the 
carina. The carina is continued a short distance beyond the posterior extremity and 
bears 2 or 3 denticles. Aborally, there is a large basal cavity, typical of Pseudopoly- 
gnathus, which extends anteriorly to the junction of the blade and platform. It is 
rounded anteriorly and pointed posteriorly. 
REMARKS. The specimen most closely resembles Pseudopolygnathus fusiformis 
Branson & Mehl, but it may be a juvenile of Polygnathus. 
Pseudopolygnathus cf. longiposticus Branson & Mehl 
Plate 30, figs. 3, 7, 9-17 
1934 Polygnathus longipostica Branson & Mehl : 294, 311, Pl. 24, figs. 8-11. 
MATERIAL. 107 specimens : figured, X 522, X 523, X 433, X 434, X 545, X 442, 
X 443, X 448, X 449, X 547. 
RANGE. Avon Gorge Z 11-C 7. 
