BRITISH AVONIAN CONODONT FAUNAS 103 
regularly ‘‘ U”’ shaped concave depression in the lateral face ; their upper termina- 
tions are bluntly pointed, and in this case they are joined to the main ridge of plat- 
form denticles by inconspicuous lateral ridges, although the denticle line is not 
broken by them. The ridge is not denticulated or ornamented in any obvious way 
in any of the three specimens. 
REMARKS. It is possible that these three forms are pathological variants of G. 
girtyi girtyi but their restriction to a single sample and the fact that all three are left 
lateral forms makes this seem unlikely. 
Gnathodus homopunctatus Ziegler 
Plate 19, figs. 5a—8d 
1957 Gnathodus commutatus punctatus Bischoff : 24, Pl. 4, figs. 7-11, 14. 
non 1957 Gnathodus commutatus punctatus Bischoff ; Ziegler in Fliigel & Ziegler : 40 (Pl. 3, 
fig. 16 = juvenile of Gnathodus bilineatus punctatus (Cooper) 1939 ; PI. 3, figs. 17, 
24=Gnathodus sp.). 
1959 Gnathodus commutatus homopunctatus [Ziegler] Voges : 281. 
1960 Gnathodus commutatus homopunctatus Ziegler : 39, 5, Pl. 4, fig. 3 (nom. nov. for 
Gnathodus commutatus punctatus Bischoff 1957 non Cooper 1939). 
1961 Gnathodus commutatus homopunctatus Ziegler ; Higgins: Pl. ro, fig. 9, text-fig. Ic. 
1962 Gnathodus commutatus homopunctatus Ziegler ; Higgins: Pl. 2, fig. 21. 
Gnathodus homopunctatus Ziegler ; Collinson & Druce in press. 
MATERIAL. 146 specimens : figured, X 120—-X 123. 
Rance. North Crop CYD 7-3D 14/15. 
DEscRIPTION. There is some similarity and degree of transition between this 
species and G. symmutatus, but the present species differs in having a relatively 
shorter and more symmetrical posterior platform, with the development of more 
conspicuous denticulation. There is some variation in this denticulation ; in 
immature specimens (e.g. Pl. 19, fig. 5c) it is barely developed, and is present only as 
rather dark, slightly elevated lateral ridges. In other specimens it tends to be 
arranged at an acute angle to the anterior part of the blade, and consists only of 
short barb-like lines of denticles. In most specimens, however, it forms more or less 
symmetrical lines of low blunt denticles, developed parallel to the outer margin of the 
platform, about midway between its lateral margin and the position of the carina. 
In most individuals the development on the two sides of the carina is equal, but in 
others it is asymmetrical. 
Gnathodus mononodosus sp. nov. 
Plate 19, figs. 13a-15d 
1961 Gnathodus commutatus var. nodosus Bischoff ; Higgins : PI. ro, fig. 7 only, text-fig. rb. 
DERIVATION OF NAME. From single node on the inner side of cup. 
Diacnosis. Straight to slightly curved blade with subcircular to sub-quad- 
rangular cup, bearing strong, generally elongate node on inner side. 
