142 BRITISH AVONIAN CONODONT FAUNAS 
The posterior bar is depressed, but is more or less straight ; it bears about 4 
denticles which are discrete, sub-triangular in profile and sharply pointed, their bases 
being confluent ; they have sharp posterior and anterior edges, feebly convex lateral 
faces, and are inclined parallel to the apical denticle, though they are not recurved 
inwardly to the same extent. The posterior bar is more shallow and slender than 
any part of the anterior bar and is only about one third to a half the length of the 
latter. 
Both bars are excavated by fine longitudinal grooves and there is a conspicuous 
flaring cavity below the apical denticle on both the inner and outer lateral faces of the 
unit, about which it is sub-symmetrical, though not symmetrical in detail, the inner 
lateral flaring occurring rather posterior to the outer lateral flaring. 
ReMmArRKs. The denticles on the anterior bar may number up to 8 in some 
specimens. The species shows some variation in the degree of lateral deflection of 
the bars in a horizontal plane. Some specimens (e.g. Pl. 24, fig. 23b) show the 
posterior bar considerably flexed outward as well as vertically. 
Lonchodina obtunda Collinson & Druce 
Plate 24, figs. 7a-c 
1957 Lonchodina projecta (Ulrich & Bassler) Ziegler in Fligel & Ziegler: 44, Pl. 4, fig. 14 
(non Pl. 5, fig. 12). 
1962 ?Lonchodina cf. projecta (Ulrich & Bassler) Higgins : Pl. 1, fig. 5. 
Lonchodina obtunda Collinson & Druce (in press). 
MATERIAL. 5 Specimens : figured, X 229. 
RANGE. North Crop 3D 8-3D 17. 
DescriPTION. The distinctive features of the species are the relatively delicate 
construction of the whole unit, the large sub-apical cavity which is developed on the 
inner lateral surface, and the very wide angle of divergence of the anterior and 
posterior bars, which in Collinson & Druce’s type specimens is I10°-135°. 
The present specimens are incomplete but they show a relatively slender anterior 
bar, with about 5 widely spaced though virtually basally confluent, denticles ; they 
are curved upward and inward and have biconvex lateral faces, the inner being the 
stronger, and relatively sharp edges. The denticles of the anterior bar range up to 
at least 5 in number. The apical denticle is strong and more or less sub-circular in 
cross-section, though it has prominent anterior and posterior edges in its proximal 
portions ; it is curved inwards and backwards, and its inner lateral face is very 
strongly expanded to give a wide flaring basal cavity which extends as a groove along 
the bars. The posterior bar is broken in the present specimens but it makes an angle 
of considerably more than go° with the anterior bar. 
REMARKS. Collinson & Druce (in press) have discussed the relationships of 
this species with other lonchodinids. 
