BRITISH AVONIAN CONODONT FAUNAS 73 
The dental units are slender with a straight, elongated, posterior bar. The 
posterior bar is about one third longer than the anterior, and has 17-24 crowded 
denticles, their apices being sharply to bluntly pointed but discrete ; they tend to be 
more or less uniform in size, though those near the distal end of the bar are slightly 
smaller than the rest of the series. The inner lateral face of the bar is flat and the 
base of the aboral edge of the bar when seen in lateral view is straight or very feebly 
convex. 
The posterior bar makes an angle of about 45° with the anterior when seen in 
lateral view : the posterior bar itself is slightly flexed inwards, although both the 
distal and proximal thirds are more or less straight. 
The anterior bar is shorter than the posterior, and its aboral edge is conspicuously 
straight. In lateral view it bears a series of crowded denticles which are confluent 
at their bases but apically discrete, and which have bluntly pointed free tips ; they 
number up to twelve and increase more or less steadily in size towards the apex. 
The apex is rounded on the aboral margin and is marked by the development of five 
rather large and conspicuous denticles, of which the three medial ones are the largest. 
They are curved inward and sometimes slightly posteriorly, but in most specimens 
they are more or less erect. They are basally confluent but apically discrete and are 
biconvex in cross-section, with sharp anterior and posterior edges, and gently convex 
lateral faces. The largest denticles tend to be large and conspicuous and, when 
viewed laterally, they tend to radiate from the apex of the arch. There is a slight 
tendency for the denticles of the posterior bar to increase in size apically. The 
whole inner lateral face of the unit is continuously recurved, although at any one 
point on the face the denticles tend to have a flat to only feebly concave surface. In 
outer lateral view the surface is feebly convex to flat and the aboral margin is marked 
by a more or less conspicuous ridge, developed on the outer lateral face. The whole 
aboral cavity is excavated below the apex. 
Remarks. The distinctive features of this species are the general form and 
curvature of the anterior and posterior bars and the development of the apical 
denticulation, in which a series of denticles, rather than any individual denticle, are 
of major size. 
Apatognathus porcatus (Hinde) 
Plate 31, fig. 27 
1900 Prioniodus porcatus Hinde : 344, Pl. ro, fig. 26. 
1928 Prioniodus porcatus Hinde ; Holmes: 22, Pl. 3, fig. 26. 
1960 Apatognathus porcata (Hinde) Clarke: 5, Pl. 1, figs. 3, 4. 
1963 non Apatognathus ? porcata (Hinde) Rexroad & Collinson : 8, Pl. 1, figs. 7-11. 
MATERIAL. 10 Specimens : figured, X 220. 
Rance. North Crop CYD 6-7, Avon Gorge C g-C 16. 
DESCRIPTION. Clarke’s diagnosis of this species, as well as his illustration of 
Hinde’s holotype, make it clear that its distinctive features are the relatively uniform 
size of the denticles, and the very strong bilateral extension of the oral surface of the 
