BRITISH AVONIAN CONODONT FAUNAS 105 
1958 Gnathodus commutatus nodosus Bischoff ; Lys & Serre : 891, Pl. 9, figs. 3a, b, 4a, b. 
1961 Gnathodus commutatus var. nodosus Bischoff ; Higgins (partim) : 213, Pl. to, figs. 8 
(non fig. 7) ; text-fig. 1b (non figs. in lower left or in uppermost left). 
1962 Gnathodus nodosus Bischoff ; Higgins: Pl. 2, fig. ro. 
1962 Gnathodus comm. nodosus Bischoff ; Meischner : 31, text-fig. 10. 
1963 Gnathodus commutatus nodosus Bischoff ; Bouckaert & Higgins : 17, fig. 3. 
Gnathodus nodosus Bischoff ; Collinson & Druce in press. 
MATERIAL. 220 specimens: figured, X 509, X 510, X 127, X 128, X 129. 
RANGE. North Crop 3D 10-3D 22. 
DESCRIPTION. This species shows some characteristics with both G. mononodosus 
and G. commutatus. These include the posteriorly restricted laterally expanded 
sub-circular to asymmetrical platform, and the rectangular lateral profile of the 
uniform blade. The distinctive feature of the present species is the development of 
denticles on both sides of the posterior platform. These are generally unevenly 
developed, the one on the inner lateral side (represented by the concave lateral 
flexure of the blade) generally being the more strongly developed of the two. Where 
the denticles are more strongly developed, they tend to make angles of 45° with the 
anterior part of the blade and to be laterally elongate. In some specimens the outer 
lateral denticle is very feebly developed in comparison with the inner, but wherever 
there is a suggestion of such bilateral denticle development, specimens are included 
in the present species. Like the other species referred to above, this species shows 
considerable but continuous variation in the symmetry and degree of lateral expan- 
sion of the posterior platform, the form of the denticles, and the relationship of the 
posterior portion of the carina to the posterior end of the platform ; there is also 
variation in the degree of lateral deflection of the blade, and the outer lateral denticle 
may also be developed posterior to the position of the inner lateral denticle. 
The blade is similar in general form to that of G. commutatus and G. mononodosus, 
having about 15 to 20 regular denticles, fused almost to their tips, and developing 
straight oral and aboral margins. There is a tendency in some specimens for the two 
anterior denticles to be relatively larger than the rest (e.g. Pl. 19, fig. 18a). The 
basal cavity is wide and flaring. 
Gnathodus punctatus (Cooper) 
Plate 18, figs. ra—c, Ioa—11d 
1939 Dyryphenotus punctatus Cooper : 386, Pl. 41, figs. 42, 43, Pl. 42, figs. 10, 11. 
1939 Dryphenotus litus Cooper : 386, Pl. 42, figs. 34, 35. 
1939 Dryphenotus macrolobus Cooper : 386, Pl. 41, figs. 48, 49; Pl. 42, figs. 45, 46. 
1939 Dryphenotus oxys Cooper : 386, Pl. 42, figs. 12, 13. 
1944 Gnathodus (Dryphenotus) macrolobus Cooper; Branson & Mehl: 245, Pl. 94, fig. 69. 
1951 Gnathodus punctatus (Cooper) Hass : 2539, Pl. 1, fig. 2. 
non 1957 Gnathodus commutatus punctatus Bischoff ; 24, Pl. 4, figs. 7-11, 14. 
1957 Gnathodus bilineatus semiglaber Ziegler in Fliigel & Ziegler : Pl. 111, fig. 23 only. 
non 1957 Gnathodus commutatus punctatus Bischoff ; Ziegler im Fliigel & Ziegler : 40, Pl. 111, 
figs. 16, 17, 24. 
1959 Gnathodus punctatus (Cooper) Hass : 395, Pl. 47, figs. 11-18. 
