70 BRITISH AVONIAN CONODONT FAUNAS 
Diacnosis. Apatognathus in which denticles on anterior bar and apical denticle 
have very conspicuous anterior and posterior keels developed on edges. They are 
unusually wide and blade-like. Two largest denticles of anterior bar separated by 
single denticle from apical denticle. Denticles of posterior bar adjacent to apical 
denticle are minute. Whole unit sharply depressed at apex and strongly inwardly 
twisted. Inner lateral faces of both bars bear conspicuous ridges near point of 
contact with denticles and are flat to concave below these ridges. 
MATERIAL. 8 specimens : Holotype X 45, Paratype X 46 (both figured). 
TYPE LOCALITY AND HORIZON. North Crop, Craig-y-dinas, Breconshire. Sample 
CYD 7. 
RANGE. North Crop CYD 7. 
DEscrIPTION. Anterior bar of unknown length ; it is deep and thin, bearing 
more than 4 strong, greatly laterally compressed denticles on its oral surface, the 
largest two being separated from the apical denticle by a single small denticle. 
The denticles of the anterior bar, as well as the apical denticle, are so strongly lat- 
erally compressed that they have strong lateral keels developed on their anterior and 
posterior edges. The combined width of these keels equals or exceeds the width of 
the ‘‘core’’ of the denticles. The denticles are basally confluent but are discrete for 
most of their lengths. They are inclined slightly posteriorly. Below the base of 
these denticles the apical bar bears a conspicuous longitudinal ledge which is rounded 
and parallels the oral surface of the bar. Below this ledge the aboral surface is 
relatively wide and there is a slight ledge developed on its inner lateral face. It is not 
conspicuously excavated. The apical denticle is strongly biconvex in cross-section 
but the anterior and posterior edges are conspicuous features on both margins. It is 
elongated, but is not conspicuously greater in width than the largest denticle on the 
anterior bar. It is straight and tapers gradually. The posterior bar is only about 
one-third the depth of the anterior, but it is thicker than it is deep. Its oral surface 
bears a series of crowded, minute and more or less sharply pointed denticles. In 
cross-section the posterior bar is more or less quadrate with a sharp longitudinal 
ridge developed on the upper inner lateral face and a more or less smooth to flat outer 
lateral face. Its basal surface is the widest part of the bar and is flat. In outer 
aie Apical denticle 
__— Outer face 
-~ Twisted distal ly 
— 
~~ Anterior bar 
Inner face 
Fic. 18. Apatognathus sp. showing morphological terms used in the text. 
Posterior bar 
