116 BRITISH AVONIAN CONODONT FAUNAS 
the posterior face is blunt and has a median groove. The apical denticle in posterior 
view is widest at the oral edge of the bar and tapers uniformly to the tip. 
The aboral surface is sharp, being broken only by a small triangular shaped pit 
directly beneath the apical denticle. 
Subgenus HIBBARDELLA (ROUND YA) Hass 1953 
TYPE SPECIES. Roundya barnettana Hass 1953. 
Hibbardella (Roundya) barnettana Hass 
Plate 25, figs. 2a—5b 
1953 Roundya barnettana Hass : 89, Pl. 16, figs. 8, 9. 
1957 Roundya barnettana Hass ; Bischoff: 52, Pl. 5, figs. 19, 20. 
1958 Roundya costata Rexroad : 26, Pl. 2, figs. 5-8. 
1961 Roundya subacoda (Gunnell) Higgins : 220, Pl. 11, fig. 13. 
1961 Roundya costata Rexroad ; Rexroad & Collinson, PI. 1. 
1962 Roundya subacoda (Gunnell) Higgins : 11, Pl. 1, fig. 1. 
1962 Roundya barnettana Hass ; Collinson, Scott & Rexroad : 12. 
MATERIAL. 14 specimens: figured, X 151, X 152, X 153, X 154. 
Rance. North Crop 3D 14/15, Avon Gorge Z 38-C 15. 
DEscRIPTION. Individuals of the present species agree closely with the very 
detailed description given by Hass (1953 : 89). They are characterized particularly 
by the massive apical denticle, with longitudinal grooves and lateral keels which are 
very prominent in the proximal portion, and sharp lateral edges which are prominent 
in the distal half. There is a conspicuous posterior concave longitudinal depression 
in the proximal quarter of the apical denticle, which becomes obsolescent towards the 
mid-point. The denticle is strongly recurved in its lower portion, but its distal 
portion is straight. The anterior bars are broken in the present specimens, but 
appear massive and bear more than two isolated denticles, which are sub-circular in 
cross-section, and curve upwards to parallel the apical denticle. The anterior bars 
diverge at an angle of about 70°—80° in the vertical plane, and the junction between 
them is rounded in anterior view. They shallow distally. The posterior bar is 
broken in the present specimens, but is clearly massive with flat to gently convex 
lateral faces, and has a convex upper surface which bears more than one erect, 
massive, sub-circular denticle. 
The aboral surface of the apical denticle is deeply excavated and the excavation 
continues along the anterior end of the posterior bars. 
Hibbardella (Roundya) sp. 
Plate 25, fig. 1 
MATERIAL. 2 Specimens: figured, X 423. 
Rance. North Crop ZLA 32. 
