BRITISH AVONIAN CONODONT FAUNAS 143 
Lonchodina paraclarki Hass 
Plate 24, figs. 16a, b 
1953 Lonchodina paraclarki Hass : 83, Pl. 16, figs. 15, 16. 
non 1958 Lonchodina paraclarki Hass ; Stanley : 468, Pl. 67, fig. 1. 
non 1958 Lonchodina cf. pavaclarki Hass ; Rexroad : 22, Pl. 4, figs. 4, 5. 
Lonchodina paraclarki Hass ; Collinson & Druce (in press). 
MATERIAL. 3 specimens: figured, X 231. 
RANGE. North Crop 3D 10-3D 14/15. 
DESCRIPTION. The most distinctive features are the very short posterior bar 
tending to develop only 2 denticles, the massive incurved and recurved apical 
denticle, and the very strong inner-lateral deflection of its aboral margin, giving a 
sub-triangular basal cavity that extends along most of the aboral surface of the unit. 
Hass has discussed the relationship of the species to Ligonodina clarki (1953 : 83) 
and Collinson & Druce have discussed the differences between Lonchodina paraclarki 
in the original sense of Hass and specimens referred to that species by Stanley & 
Rexroad. 
Lonchodina paraclaviger Rexroad 
Plate 24, figs. 15a, b, 18a, b 
1958 Lonchodina paraclaviger Rexroad : 22, Pl. 4, figs. 7-10. 
Lonchodina paraclavigey Rexroad ; Collinson & Druce (in press). 
MATERIAL. 780 specimens : figured X 232, X 233. 
RANGE. North Crop 3D 13-3D 14/15. 
DEScRIPTION. This species is characterized by its stout general construction. 
The posterior bar is about half the length of the anterior bar. The stout, basally 
confluent, elongated, pointed denticles, number eight on the anterior bar, and four on 
the posterior. Both bars are straight except for slight curvature in the anterior, 
where they make an angle of about g0°-100° with each other. The lateral deflection 
of the posterior bar is about 45° out of the vertical plane of the anterior bar, and a 
large flaring asymmetrical cavity is strongly developed on the inner side, as a sub- 
triangular, to rounded expansion, that is flat on the outer lateral face and is extended 
along both bars as a deep groove. Both bars are relatively deep, with convex lateral 
faces. The denticles of the anterior bar, although basally confluent, are discrete for 
most of their length, and approach the apical denticle in size ; they may be of 
uniform size or they may increase in size towards the anterior end of the unit ; they 
are slightly recurved posteriorly and also inwardly, and lie more or less parallel to the 
apical denticle, which is sometimes only slightly larger than those of the anterior bar. 
The apical denticle is very strongly convex on its inner lateral face, with sharp 
anterior and posterior edges, and rather less strongly convex on its outer lateral face ; 
it is more or less straight in lateral view but is inclined posteriorly at about 60° to the 
anterior bar and is also recurved inwardly. The denticles of the posterior bar tend 
