BRITISH AVONIAN CONODONT FAUNAS 17I 
denticles at the anterior end of the bar are more or less erect, but those toward the 
posterior end become increasingly strongly inclined posteriorly. In a few specimens 
the denticles at the anterior end of the bar are also posteriorly inclined. The lateral 
faces of the anterior bar are flat to gently convex, the convexity increasing in the 
posterior half of the bar. The apical denticle is variable in size and in inclination. 
It is of similar form to the denticles of the anterior bar and its free portion is sharply 
pointed, with sharp, straight anterior and posterior edges. It is strongly inclined at 
an angle of up to about 50° to the posterior bar, and is from one and a half to three 
times as wide and about twice as long as the largest adjacent denticles. In some 
specimens the denticles of the anterior bar are more widely spaced and appear almost 
discrete, but in most specimens they are more or less confluent. 
The posterior bar is depressed with respect to the anterior, and the whole aboral 
surface is either continuously and gently concave, or both the anterior and posterior 
bars may be more or less straight and meet at an angle of about 120°. (This is the 
projected angle made by their straight distal ends in those specimens where the lower 
surface is strongly arched). The posterior bar bears 10 or more laterally compressed 
closely spaced denticles, which, although in some specimens they are more or less 
equal in size, show a marked decrease in size in the posterior quarter of the bar in 
others. They are generally rather smaller than the denticles of the anterior bar and 
fewer in number. In some specimens the posterior bar, and to a lesser extent the 
anterior bar, are strongly flexed inwards. The denticles of the posterior bar are all 
inclined at about 50° to the posterior bar itself. 
In aboral view the unit has a rather conspicuously flattened aboral margin, which 
decreases in width towards the anterior and posterior ends of the unit. There is a 
continuous longitudinal slit along both limbs, and a slightly flared median cavity 
below the apical denticle, which is continuous with the slit. The flaring of this cavity 
is not a conspicuous feature, but the thickened lips of the main longitudinal cavity 
are more or less conspicuous in aboral view. 
This species shows some variation in the degree of flexing of the anterior and 
posterior bars in a vertical plane and in the relative depth and detailed denticulation 
of the anterior bar. Specimens illustrating various morphological variations are 
illustrated. 
Ozarkodina hindei Clarke 
Plate, 27 figs. 16, 17, 22 
1879 Polygnathus dubius Hinde : 363, Pl. 16, fig. 8 only. 
1900 Polygnathus dubius Hinde ; Hinde: 341, Pl. 9, fig. 1 only. 
1928 Prioniodina (Polygnathus) dubius (Hinde) Holmes : 109, PI. 8, fig. 1 only. 
1960 Ozarkodina hindei Clarke : 18, Pl. 3, figs. 1, 6. 
1961 Ozarkodina compressa Rexroad ; Rexroad & Burton: PI. 141, fig. 16 only. 
MATERIAL. 3 specimens : figured, X 294, X 293, X 295. 
Rance. North Crop 3D 6-3D 12. 
DEscrRIPTION. The diagnostic features of this species are the very deep and 
strongly laterally compressed anterior and posterior bars, and the very wide, short 
