BRITISH AVONIAN CONODONT FAUNAS 77 
denticles, standing perpendicular to the bar, the largest developed at about midpoint. 
The basal cavity is minute and is situated beneath the apical denticle. 
REMARKS. This form is very similar to A patognathus? geminus (Hinde) of Rexroad 
and Collinson (1963), our specimens differing only in that the posterior bar is more 
strongly curved and twisted. This may not be specifically significant, and if the two 
forms are identical, the range of the present form would be extended upward, into the 
St. Louis Formation of the Upper Mississippi Valley. Rexroad and Collinson 
(1963 : 7) point out that in North America there is a gap between the Upper 
Devonian and Upper Viséan record of Apatognathus. Our apatognathid fauna 
appears to bridge that gap, and thus Apatognathus may not necessarily be a poly- 
phyletic genus as Rexroad and Collinson suggest. 
Apatognathus sp. 
Plate 31, fig. 2 
MATERIAL. 16 specimens : figured, X 318. 
Rance. Avon Gorge Z 36—D 32. 
DESCRIPTION. Fragmentary apatognathids occur in various parts of the succes- 
sion. The specimen illustrated represents one such form, though other broken 
specimens show considerable variation. They are not sufficiently complete to make 
it possible to refer them to individual species. 
Genus CAVUSGNATHUS Harris & Hollingsworth 1933 
1933 Cavusgnathus Harris & Hollingsworth : 200-201. 
TYPE SPECIES. Cavusgnathus alta Harris and Hollingsworth 1933. 
DescripTiIon. Harris and Hollingsworth (1933) gave the following description 
for the genus : ‘This genus is erected to include those lanceolate plated conodonts 
with no semblance of a median crest in the median oral channel. Outline of plate 
lanceolate to claviform ; oral face of plate with complete, deep, median longitudinal 
channel without crest and bordered by marginal rims ornamented with denticles, 
nodes, corrugations, or combinations of the same ; posterior bar denticulate’. 
Ellison (1941) gave the following revised description : ‘Elongate platform-like 
teeth with high sides, extending parapet-like above a median longitudinal trench, 
one parapet continued into a free longitudinal blade and connected at the posterior 
end to opposite parapet, whose length is limited by the length of the platform ; 
aboral surface of platform smooth, deeply excavated as a longitudinally elongate, 
laterally asymmetrical spathodid-like cup, pointed at each end, transversed by a 
median longitudinal groove, which extends to the ends of the platform and along the 
aboral edge of blade ; sides of platform somewhat constricted laterally above the 
aboral margin, to produce a lip-like lateral margin of variable width ; oral surface of 
platform more or less grooved transversely, oral edge of blade denticulate and 
crenulate. 
