76 BRITISH AVONIAN CONODONT FAUNAS 
symmetry. In the present specimen the two limbs diverge at an angle of about 45° 
in outer lateral view. The denticles stand more or less erect to the limbs towards 
their distal extremities but they tend to radiate away from the apex ; they are 
more or less sub-equal in size and closely similar in size on both anterior and posterior 
bars. The apical denticle tends to be only slightly larger than the largest on the 
bars, on which the largest denticles tend to be separated by a single denticle from 
both the anterior and posterior edges of the apical denticle. The denticles are 
confluent for about two-thirds of their length, with sharp anterior and posterior 
edges and gently convex lateral faces. The whole unit is continuously recurved 
inward and on both the anterior and posterior limbs there is a more or less con- 
spicuous basal longitudinal ridge developed near the aboral margin. In inner lateral 
view the whole unit is regularly and continuously concave. The bars of the present 
specimens are of rather unequal length, the anterior bearing g denticles and the 
posterior 8 ; it is probable that neither is complete, however. 
REMARKS. The present specimen bears a very close resemblance to Varker’s 
holotype in all features except the relative size of the apical denticle. In the present 
specimen this is only about half the size of that in Varker’s specimens. This does 
not seem to us, at present, a valid reason for regarding the two forms as distinct 
species. Varker notes that the processes of his specimens bear up to 20 or more 
denticles. 
We have used the name of this species as the zonal name for one of our zones. 
The zone is characterized by the common occurrence of apatognathids, virtually all 
of which are broken, however. Many of these resemble the present species, but they 
are too fragmentary to include in the count of material. 
Apatognathus sp. nov. A 
Plate 31, fig. 22 
MATERIAL. 2 Specimens : figured, X 43. 
TYPE LOCALITY AND HORIZON. North Crop, River Clydach, Nr. Gilwern, Z Zone. 
Sample ZLA 13. 
RANGE. North Crop ZLA 13. 
Description. A strongly arched Apatognathus with conspicuous apical denticle. 
Slender recurved anterior bar has about 10 crowded denticles, and is curved in the 
same plane as the apical denticle. Posterior bar stout, deep, deflected and depressed, 
with 4-5 large, discrete denticles. 
The unit is arched and bowed. The apical denticle is tall, laterally compressed, 
with knife edges on the anterior and posterior margins, posteriorly recurved and 
laterally inclined toward the inner side. The outer face is strongly, and the inner 
face feebly, convex. The anterior bar lies in the same plane as the apical denticle 
and is shallow and somewhat recurved. It bears about ro laterally compressed, 
posteriorly inclined, partially fused denticles. The deep posterior bar is deflected, 
and depressed. It bears a series of 4 or 5 large, discrete, laterally compressed 
