BRITISH AVONIAN CONODONT FAUNAS 163 
1958 Neoprioniodus scitulus (Branson & Mehl) Rexroad : 23, 24, Pl. 5, figs. 10-14. 
1959 Neoprioniodus scitulus (Branson & Mehl) Elias: 151, Pl. 2, figs. 6, 7. 
1959 Neoprioniodus cassilaris (Branson & Mehl) Elias : 153, Pl. 2, figs. 20, 21 only. 
1961 Neoprioniodus scitulus (Branson & Mehl) Higgins :; 220, Pl. 11, fig. 1. 
1961 Neoprioniodus scitulus (Branson & Mehl) Rexroad & Burton : 1155, Pl. 140, figs. 15-17. 
1963 Neoprvioniodus scitulus (Branson & Mehl) Bouckaert & Higgins : 17, fig. 3. 
1963 Neoprioniodus scitulus (Branson & Mehl) Thompson & Goebel : 12, fig. 3. 
1964 Neoprioniodus scitulus (Branson & Mehl) Rexroad & Furnish : 674, Pl. 111, figs. 36, 37. 
1965 Neoprioniodus scitulus (Branson & Mehl) Rexroad & Nicoll : 23, 24, Pl. 2, figs. 21, 22. 
Neoprioniodus scitulus (Branson & Mehl) Collinson & Druce (in press), Pl. 2, fig. 1. 
MATERIAL. 24 specimens : figured, X 276, X 277, X 278. 
RANGE. North Crop 3D 2-3D 14/15. 
DESCRIPTION. This is a variable species which, as Rexroad (1958 : 23) has 
demonstrated, shows appreciable variation during ontogeny in the relative curvature 
of the anterior denticle, the length of the aboral projection and the outline of the 
aboral margin. The basal cavity is also variable, and tends to be filled in during 
growth, ultimately resulting in a minute pit, with a longitudinal median groove 
extending anteriorly and posteriorly from it. There are also smaller differences in 
the form and denticulation of the posterior bar, which are shown by numbers of well- 
preserved specimens in the present faunas. In younger individuals the posterior 
inclination of the denticles of the posterior bar tends to be correspondingly greater 
than that in older individuals, but this, as well as the other variations, seem to fall 
within the limits of Branson & Mehl’s species. 
c 
REMARKS. The variation in “ another prioniodid’’ mentioned by Branson & 
Mehl (1940 : 174) as including a minute pit and attachment scars on the lateral faces 
of the anterior denticle, seem to fall within the variation of the present species, 
rather than representing a distinct species as they suggest. The most striking 
general features of the present species are the long slender elegant anterior denticle, 
the rather short finely pointed aboral process, and the relatively slender, straight to 
slightly curved posterior bar, together with a general lack of flaring in the lateral 
faces below the anterior denticle. 
Neoprioniodus spathatus Higgins 
Plate 21, figs. ga, b 
1961 Neoprioniodus spathatus Higgins : 217, Pl. 11, figs. 2, 4, text-fig. 5. 
MATERIAL. I specimen : figured, X 279. 
Rance. North Crop 3D 14/15. 
DEscrRIPTION. The diagnostic feature of this species is the spatulate plough-like 
form of the aboral process, which projects with conspicuously concave lateral faces 
and strongly laterally extended basal surfaces. It has a denticulated anterior edge. 
The anterior denticle is relatively strongly developed. Its inner lateral face is flat 
to very feebly convex, but its outer lateral face is more strongly convex. It has very 
sharp anterior and posterior edges and is laterally twisted and slightly inwardly 
