218 BRITISH AVONIAN CONODONT FAUNAS 
Pseudopolygnathus sp. A 
Plate 6, fig. 3 
MATERIAL. 61 specimens : figured, X 515. 
RANGE. North Crop ZLA 29-ZLA 32. 
DeEscrIPTION. The specimen illustrated is very long and narrow. The platform 
is extremely variable in its development and always highly irregular in outline. 
Often it consists of irregular nodes rising out of the thickened medial part of the 
unit ; sometimes these are fused to give a nodose platform of 3 to 4 denticles on 
either side of the carina. Occasionally there are no nodes on the medial thickening. 
The carina is very distinctive, consisting of sub-circular needle-like denticles standing 
high above the platform. The anterior blade is very long and is a continuation of 
the carina. In aboral view the basal cavity is elongate and asymmetrically flared. 
Genus SCAPHIGNATHUS Ziegler 1960 
1960 Scaphignathus Ziegler : 403. 
TYPE SPECIES. Scaphignathus velifera Ziegler 1960. 
The generic name and the type species were used, and the latter described, by 
Helms (1959 : 655) who referred both to Ziegler 1959 as author. Ziegler’s paper was 
not published until 1960, but subsequent authors have also attributed the genus to 
him, and we follow this practice, which Article 50 of the Code of Zoological Nomen- 
clature clearly allows. 
Scaphignathus ? sp. A 
Plate 2, figs. 13a-c 
MATERIAL. I specimen : figured, X 532. 
RANGE. North Crop ZL 2. 
DeEscripTION. The unit is boat-shaped, being asymmetrical with the anterior 
blade developed on the right hand side when viewed posteriorly. The anterior blade 
is broken in the only specimen. The platform is lanceolate, being widest at the 
anterior, and is triangular in cross-section in the posterior portion. It is over twice 
as long as wide, and is ornamented with low transverse ridges, terminating in low 
nodes on the platform edge. Along the mid-line there runs a low nodose carina, 
which joins the inner edge immediately posterior to the outer lateral blade, and then 
runs as a low ridge anteriorly, joining the outer lateral blade and thus preventing the 
trough from opening anteriorly. 
In aboral view the cavity is large and asymmetrical, being expanded on the inner 
side : the posterior part of the platform has a keel with a median groove. 
REMARKS. This form differs from Scaphignathus ? sp. B in that the oral trough 
does not open anteriorly. The reasons for placing these two forms tentatively in the 
genus Scaphignathus are given in the remarks following the description of S. sp. B. 
