BRITISH AVONIAN CONODONT FAUNAS 139 
Ligonodina tulensis (Pander) 
Plate 31, fig. 9 
1856 Prioniodus tulensis Pander (partim) : 30, tab. 2a, fig. 19 only. 
1900 Prioniodus tulensis Pander ; Hinde (partim) : 343, Pl. 9, fig. 15 only. 
1928 Prioniodus tulensis Pander ; Holmes (partim) : 22, Pl. 3, fig. 22 only. 
MATERIAL. 6 specimens : figured X 328. 
RANGE. North Crop CYD 6-CYD 7. 
DeEscriPTion. The present specimens are fragmentary but they display most of 
the features described by Clarke. The main denticle tends to be rather large in 
comparison with the size of the posterior bar ; its lateral faces are flat to gently 
convex, and in its lower portion the anterior and posterior edges tend to be blunted. 
The denticles of the posterior bar are relatively small, and are discrete. The anterior 
aboral process is strongly recurved laterally, and is also twisted, so that the denticles 
are directed anteriorly. Its distal end makes a right angle in a horizontal plane with 
the posterior bar. The denticles of the process tend to be rather larger than those 
of the posterior bar. 
Ligonodina sp. A 
Plate 26, figs. 3a—c 
MATERIAL. I0 specimens : figured, X 217. 
RANGE. North Crop ZLA 32-ZLA 33. 
Description. All the present specimens are broken, but the species appears to be 
a ligonodinid with a greatly excavated main denticle. The main denticle itself is 
massive, sub-circular in cross-section, with a sharp lateral costa developed in line 
with the anterior aboral process. The antero-aboral process is broken, but the 
posterior bar can be seen to be short, bearing three tall isolated denticles, and having 
its aboral side grooved. 
REMARKS. The overall appearance of this species is of a Rowndya with only one 
limb of the anterior arch developed. Youngquist, Miller & Downs (1950 : 527) 
illustrate and describe similar forms as Ligonodina? sp. Our material is too frag- 
mentary for a specific designation but it would appear that the two forms may be 
conspecific. 
Ligonodina ? sp. 
Plate 26, fig. 7 
MATERIAL. I specimen : figured, X 218. 
RANGE. North Crop ZLA 11. 
DEscripTION. This appears to be a pathological form of L. beata. There is a 
secondary lateral process developed on the inner side of the posterior bar and it bears 
one low node. The angle of the process, and its inclination toward the posterior, are 
parallel to that of the antero-aboral process. The basal cavity is extended along it 
on the aboral side. 
