BRITISH AVONIAN CONODONT FAUNAS o 113 
Hibbardella (Hibbardella) milleri Rexroad 
Plate 25, figs. 23a-25b 
1957 Hibbardella n. sp ? Rexroad : 31, Pl. 1, fig. 19. 
1958 Hibbardella milleri Rexroad : 18, Pl. 2, figs. 13-16. 
1960 Hibbardella milleri Rexroad ; Clarke: 6, Pl. 1, fig. 6. 
1961 MHibbardella milleri Rexroad ; Higgins: Pl. 12, fig. 7. 
1961 AHibbardella milleri Rexroad ; Rexroad & Burton: 1153, Pl. 140, figs. 3, 4. 
1964 Hibbardella millevi Rexroad ; Rexroad & Furnish : 671, Pl. 111, fig. 17. 
1965 Hibbardella millevri Rexroad ; Rexroad & Nicoll: 19, Pl. 1, fig. 13. 
MATERIAL. 3 Specimens: figured, X 140, X 141, X 142. 
RANGE. North Crop 3D 14/15. 
DEscRIPTION. Individual specimens of this species bear a strong resemblance to 
those described by Rexroad, but differ from his description in having no denticle 
developed anterior to the apical denticle. The most characteristic features of 
individuals are the short, deep and obtusely divergent anterior bars, the distal ends 
of which are spatulate to sharply pointed. The denticles of the anterior bars are 
massive, increasing in size distally and numbering 3 or 4. They are more or less 
anteriorly compressed and sharp edged. The apical denticle is massive, elongate, 
sub-circular to oval in cross-section ; in some specimens it is very elongate (e.g. 
Pl. 25, fig. 24). In well preserved specimens the apical denticle is sharply pointed at 
its distal end, and is sub-circular in cross-section. In the proximal third its posterior 
surface is marked by either a very faint groove or a very faint depression. The 
posterior bar is short, narrow and deep, with two or three small, isolated denticles on 
its oral surface. 
The basal cavity is developed as shallow grooves which run along the posterior and 
the anterior bars, and the base of the apical denticle is slightly excavated. The 
aboral groove does not extend the whole length of the anterior bars, and the posterior 
groove decreases in width and depth posteriorly. 
Hibbardella (Hibbardella) ortha Rexroad 
Plate 25, figs. 22a, b 
1900 Prioniodus angulatus Hinde (partim) : 343, Pl. ro, fig. 18 (non fig. 19). 
non 1926 Hibbardella angulata (Hinde) Ulrich & Bassler : 37, Pl. 3, figs. 1-4. 
1928 Hubbardella angulata (Hinde) ; Holmes: 11, Pl. 4, fig. 32. 
1958 Hibbardella ortha Rexroad : 18, Pl. 2, figs. 9-12. 
1960 HAibbardella ovtha Rexroad ; Clarke: 6, Pl. 1, fig. 7. 
1961 Hubbardella ortha Rexroad ; Rexroad & Burton : 1153, Pl. 140, figs. 5, 6. 
1964 Hibbardella ovtha Rexroad ; Rexroad & Furnish : 671, Pl. 111, fig. 16. 
1965 Hibbardella ortha Rexroad ; Rexroad & Nicoll: 19, Pl. I, fig. 12. 
Hibbardella orvtha Rexroad ; Collinson & Druce in press. 
MATERIAL. 780 specimens : figured, X 143. 
RANGE. North Crop 3D 10-3D 22. 
DESCRIPTION. The present specimens are more complete than those described by 
