140 BRITISH AVONIAN CONODONT FAUNAS 
Ligonodina ? sp. 
Plate 26, figs. 12a—b 
MATERIAL. I specimen : figured, X 219. 
RANGE. North Crop 3D to. 
DeEscripTION. This single specimen is presumably a pathological form of the 
genus Ligonodina. It is characterized by the presence of the antero-aboral process 
and by the fact that the main denticle can just be discerned when the lighting is 
favourable. On the posterior edge of this denticle, however, and continuous with it, 
there is a sheet-like development of conodont material which extends in the same 
plane as the posterior bar. Only the anterior denticle is visible within this by 
reflected light. The denticles of the antero-aboral process are sub-circular in form, 
3 in number, and discrete, the middle one of the three being the largest. The form 
of the outer lateral face of the extension of the anterior denticle suggests that the 
conodont was attached by this surface ; this then became an aboral surface although 
in “‘ normal” specimens it would have represented an upper lateral surface. 
Genus LONCHODINA Ulrich & Bassler 1926 
1925 Lonchodina Bassler : 219 (nom. nud.). 
1926 Lonchodina Ulrich & Bassler : 
TYPE SPECIES. Lonchodina typicalis Ulrich & Bassler 1926. 
Lonchodina bolbosa Collinson & Druce 
Plate 24, figs. 12a-14b 
1957 Lonchodina nitela Huddle ; Ziegler in Fliigel & Ziegler : 44, Pl. 4, fig. ro. 
1961 Lonchodina cf. projecta (Ulrich & Bassler) Higgins ; 220, Pl. XI, fig. ro. 
Lonchodina bolbosa Collinson & Druce (in press). 
MATERIAL. 12 Specimens : figured, X 223, X 222, X 224. 
RanGE. North Crop 3D 8-3D 14/15. 
DESCRIPTION. The distinctive features of this species are the relatively sub-equal 
short and rather slender bars, the conspicuous basal flaring below the apical denticle 
on the outer lateral face and the divergence of the two bars below the denticle at an 
angle of more than go° ; in some specimens the angle approaches a right angle, but 
in others, the angle may be as high as 110°. 
The present specimens are very fragmentary but they show the long recurved, 
laterally compressed apical denticle, the distinctive flaring cavity, and the straight 
and relatively short anterior aboral process described by Collinson & Druce. The 
basal excavation below the main denticle is large but shallow, and is extended as a 
very narrow groove along the anterior aboral process. 
