198 BRITISH AVONIAN CONODONT FAUNAS 
Prioniodina stipans (Rexroad) 
Plate 28, figs. 7a—1oc 
1957 Subbryantodus stipans Rexroad : 39, Pl. 4, fig. 1. 
1961 Swubbryantodus stipans Rexroad ; Higgins: 219, text-fig. 6, Pl. 12, fig. 14. 
1962 Subbryantodus stipans Rexroad ; Higgins : 13, text-fig. 2, Pl. 1, fig. 9. 
MATERIAL. 105 specimens : figured, X 337—X 340. 
RANGE. North Crop 3D 10-3D 22. 
DescripPTION. The most distinctive features of this species are the relatively 
short but strongly curved general form, with a series of subequal pointed denticles, 
the apical denticle being only slightly larger than those of its neighbours, and the 
wide flaring and greatly longitudinally extended basal cavity. 
The basal cavity is greatly elongated and extends almost to the posterior end of the 
posterior bar, and about two-thirds the way to the end of the anterior bar. It is 
biconvex in outline, very deep, and slightly asymmetrical, with thin lateral edges. 
The anterior bar is about equal in length to the posterior, but is rather deeper, 
although it decreases slightly in depth anteriorly. The whole basal margin of the 
unit is deeply concave in inner lateral view and the anterior bar is conspicuously 
bowed inward. There is a rather inconspicuous shoulder developed about two-thirds 
of the height from the aboral margin to the base of the denticles. The anterior bar 
bears a series of about 12 denticles, confluent for most of their length, but bluntly 
pointed in their free apices. They have strongly convex lateral faces in their free 
portions and flat to gently convex lateral faces in their confluent portions, their free 
edges being more or less sharp. Those in the posterior two-thirds of the bar are of 
more or less uniform height and are regularly inclined posteriorly at about 45° to the 
bar, but those in the anterior third of the bar decrease in height towards the anterior 
end, and the most anterior two or three denticles are relatively inconspicuous and 
wholly confluent. 
The apical denticle is about twice as wide as the adjacent denticles, and is about 
twice as long as adjacent denticles of the anterior and posterior bars. It is inclined 
at about 45° to the adjacent aboral surface. 
The posterior bar is sharply recurved and bears a series of about 7 sharply pointed 
and partly fused denticles, which are strongly laterally compressed, and which tend 
to decrease in size posteriorly, especially in the posterior third. 
Prioniodina subaequalis (Higgins) 
Plate 28, figs. Ia—4 
1961 Subbryantodus subaequalis Higgins : 218-2109, Pl. 12, fig. 15, text-fig. 6. 
1963 Subbryantodus subaequalis Higgins ; Bouckaert & Higgins : 17, fig. 3. 
Subbryantodus subaequalis Higgins ; Collinson & Druce (in press). 
MATERIAL. 143 specimens : figured, X 341—X 344. 
RANGE. North Crop 3D 10-3D 22. 
