212 BRITISH AVONIAN CONODONT FAUNAS 
anterior blade is also equal in height to its length, and is curved in the opposite 
direction to the curvature of the posterior extension of the carina. The basal cavity, 
situated in the anterior part of the unit, is subcircular in outline, but more drawn out 
to the posterior than the anterior. It is as wide as the platform in juveniles, but in 
adults is less wide than the platform. 
REMARKS. This species developed from Pseudopolygnathus primus by the extension 
of the nodes on the left side of the platform towards the anterior, and by a change in 
the platform ornament from marginal nodes to transverse ridges. 
Pseudopolygnathus striatus, P. rusticus, P. attenuatus and P. lanceolatus are all 
considered to be growth stages of P. multistriatus. P. striatus is a homoeomorph of 
P. dentilineatus, as pointed out by Klapper (1966 : 15). 
Lower Z forms referred to P. dentilineatus in this study (PI. 6, fig. 8) resemble P. 
multistriatus (Pl. 5, fig. 16), but the left side of the platform is more strongly 
developed, and also there are 8 nodes or ridges on the right side of the platform in 
P. multistriatus. 
The Avonian P. multistriatus pseudopolygnathids gave rise to P. cf. longiposticus. 
Pseudopolygnathus nodomarginatus (E. R. Branson) 
Plate 9, figs. ra—4c. Plate 12, figs. 6a—8c, I0a—c 
1934 Polygnathus nodomarginata E. R. Branson 310, Pl. 25, fig. ro. 
1934 Pseudopolygnathus brevimarginata E. R. Branson 322, Pl. 26, fig. 3. 
1934 Pseudopolygnathus tenuis E. R. Branson 319, Pl. 26, figs. 13, 14. 
1938 Polygnathus flabella Branson & Mehl: 147, Pl. 34, fig. 48. 
1939 Polygnathus anida Cooper : 399, Pl. 39, figs. 39, 40. 
1939 Polygnathus flabellum Branson & Mehl ; Cooper : 400, Pl. 39, figs. 13, 14. 
1944 Polygnathus flabella Branson & Mehl; E. B. Branson : 208, 221, Pl. 39, fig. 48. 
1949 Polygnathus anida Cooper ; Thomas: 411, Pl. 3, figs. ro, 11. 
1950 Streptognathodus ? sp. Youngquist, Miller & Downs : 529, Pl. 67, figs. 12-14. 
1951 Polygnathus aff. symmetrica Branson & Mehl ; Youngquist & Downs : 789, Pl. 111, 
fig. 6. 
1956 Polygnathus inornata E. R. Branson ; Bischoff & Ziegler : 157, Pl. 12, figs. 4, 5. 
1957 Polygnathus nodomarginata E. R. Branson ; Bischoff & Ziegler : 157, Pl. 12, fig. 6. 
1959 Polygnathus cf. flabellum Branson & Mehl ; Voges: 290, Pl. 34, figs. 8-11. 
non 1959 Polygnathus nodomarginata E. R. Branson ; Helms: 251, Pl. 3, figs. 1a, b, c. 
1966 Polygnathus nodomarginata E. R. Branson ; Jones & Druce: 358, fig. 3, No. 3. 
MATERIAL. 323 Specimens : figured, X 488, X 489, X 490, X 491, X 492, X 493, 
X 494, X 495. 
RANGE. North Crop ZLA 29-ZL 18. 
DescriPTIONn. The platform is asymmetrical, one side being shorter than the 
other. In juveniles it is ornamented by a lateral row of nodes on each margin with a 
trough on either side of the medial carina (PI. 9, fig. 1). With old age the rows of nodes 
expand into a platform with transverse ridges and the troughs tend to shallow (e.g. 
Pl. 12, fig. 6a). The carina is coarsely nodose and extends posteriorly, the juveniles 
often exhibiting a longer posterior free blade than the adults. The anterior blade is 
about half the platform length ; the highest denticles are developed anteriorly and 
