162 BRITISH AVONIAN CONODONT FAUNAS 
1957 Prioniodina cassilaris (Branson & Mehl) Bischoff : 46, Pl. 5, figs. 27-31. 
1960 Neoprioniodus peracutus (Hinde) Clarke : 14, Pl. 2, fig. 6. 
1964 Neoprioniodus peracutus (Hinde) Rexroad & Furnish : 674, Pl. 111, fig. 25. 
MATERIAL. 32 Specimens : figured, X 272, X 273, X 274, X 275. 
RANGE. North Crop 3D 4-3D 22. 
DescripTIon. A slender neoprioniodid in which the anterior denticle is continued 
more or less vertically downward to form the aboral process. There is a slender and 
highly recurved posterior bar, the straight postero-aboral portion of which makes an 
angle of about 130° with the posterior edge of the anterior denticle. The posterior 
bar decreases in depth posteriorly, its posterior termination being bluntly pointed, 
its antero-aboral surfaces gently concave, and its postero-aboral surface gently 
convex in lateral view. In outer lateral view its face is flat, and the whole unit is 
curved slightly inward so that its inner margin is concave. The oral surface of the 
posterior bar bears about 19 denticles which tend to decrease in height posteriorly. 
They are basally confluent, but apically discrete, being bluntly pointed, with sharp 
anterior and posterior edges and convex lateral faces. The denticles tend to be most 
conspicuously discrete in the anterior third of the bar, those towards the posterior 
portion being coalesced for the greater part of their length, but being discrete in their 
apical region. 
The anterior denticle is slightly offset inwardly from the main line of the posterior 
denticles. It has sharp anterior and posterior edges, a feebly convex outer lateral 
face, and a rather flat antero-inner surface which extends downwards into the flat 
aboral process. The anterior edge of the aboral process is more or less straight, and 
the posterior aboral edge is regularly but feebly convex, giving the whole aboral 
extension a slender plough-like appearance. In inner lateral view, the inward 
deflection and curvature of the anterior denticle are well seen ; the antero-aboral 
face of the anterior denticle tends to be slightly concave, but otherwise the inner 
lateral face is more or less flat to feebly convex in its upper portion. Its anterior 
aboral edge bears two minor irregularities, but these are not sufficiently distinct to be 
recognized as denticles. The interior aboral edge of the anterior denticle is 
expanded, but not strongly so, and there is a very shallow longitudinal pit developed 
which extends along the flattened basal surface of the posterior bar ; the anterior 
part of the denticle has longitudinal slit-like grooves. 
Neoprioniodus scitulus (Branson & Mehl) 
Plate, 22, figs. ga—1ob, 12a, b 
1939 Prioniodus peracutus Cooper : 406, Pl. 46, fig. 7. 
1940 Prioniodus scitulus Branson & Mehl : 173, Pl. 5, figs. 5, 6. 
1947 Prioniodus scitulus Branson & Mehl ; Cooper: 92, Pl. 20, figs. 1-3. 
1949 Prioniodus spp. Youngquist & Miller : 62, Pl. ro1, figs. 9, 10, 14. 
1956 Prioniodus scitulus Branson & Mehl ; Elias: tog, Pl. 2, figs. 9, 10. 
1957 Neoprioniodus scitulus (Branson & Mehl) Rexroad : 35, Pl. 2, figs. 22, 26. 
1957 Neoprioniodus striatus (Branson & Mehl) Rexroad : 35, Pl. 2, figs. 11, 12. 
1957 Prioniodina cassilaris Branson & Mehl ; Bischoff : 46, 47, Pl. 5, figs. 27-31. 
