68 BRITISH AVONIAN CONODONT FAUNAS 
posterior and the anterior extremities. The apical denticle is of the same size as the 
denticles of the anterior bar. The anterior bar is short, depressed downward through 
70° and deflected inward up to go°. It bears isolated sub-circular denticles, which 
tend to increase in size anteriorly. The posterior bar is about four to five times as 
long as the anterior bar. It is deflected through about go° at its posterior termina- 
tion, and bears irregular, isolated, sub-circular denticles, which increase in size 
posteriorly to the point of depression, when they decrease in size towards the 
posterior end. Those in the anterior portion of the posterior bar bear smaller 
denticles (about one third the width of the larger ones) between them. In aboral 
view the unit is excavated beneath the apical denticle and possesses an inverted basal 
cavity over its whole length. Here and elsewhere “‘ inverted ”’ is used to describe a 
basal cavity with wide flaring opening and more or less restricted internal form (see 
Lindstrém 1964). This is visible as a basal flange in lateral view. 
Angulodus sp. nov. C 
Plate 29, figs. 3a—4c 
MATERIAL. 18 specimens : figured, X 38, X 39. 
LOCALITY AND HORIZON. North Crop, River Clydach, Nr. Gilwern, K and Lower 
Z Zones. Sample ZLA Io. 
RANGE. North Crop KL 1-ZLA 14, Avon Gorge Z 34-Z 38. 
DeEscrRIPTION. A simple, stout, short unit, with a few stout, isolated denticles ; 
bars are deflected and depressed in at least two directions on the inner side. 
The apical denticle is relatively small, sub-circular in cross-section, posteriorly 
inclined and continuously curved at various angles towards the inner side. The 
short, stout anterior bar is deflected through 90° and then depressed downward 
through go°. It bears 3 to 4 massive, discrete, sub-circular denticles, which tend to 
decrease in size distally. The posterior bar is massive and very short, the anterior 
portion being about equal in length to the anterior bar and only slightly longer than 
the posterior portion. It is stout, with broadly convex lateral faces, and is slightly 
twisted. The posterior depression may be strong or gentle, but the distal end is 
depressed through about go° in both cases. It bears only 3 to 5 stout, sub-circular, 
posteriorly inclined, isolated denticles, the largest being at the point of depression. 
In aboral view the unit is expanded, the cavity being large and extremely shallow, 
in some cases approaching an inverted basal cavity ; it is largely confined to the 
anterior portion of the posterior bar (PI. 29, fig. 3c). 
REMARKS. This is a very unusual form, the only comparable species being 
Centrognathodus spurius Branson & Mehl (1934 : 198). The present specimens differ 
from this in the relative position of the basal cavity and the lack of an “‘ outer spur ”’. 
A form described as Angulodus demissus Huddle by Bischoff & Ziegler (1957 : 43) is 
also similar. This latter form, which is not Angulodus demissus Huddle, could be 
the same as our specimens. Angulodus sp. C differs from Angulodus sp. D in the 
nature of the posterior termination. 
