238 BRITISH AVONIAN CONODONT FAUNAS 
Spathognathodus ziegleri sp. nov. 
Plate 4, figs. 5a—8d 
non 1934 Spathodus spinulicostatus E. R. Branson : 305, Pl. 27, fig. 19 [= S. sulciferus]. 
1956 Spathognathodus spinulicostatus (E. R. Branson) Bischoff & Ziegler : 167, Pl. 13, 
fig. 7. 
1957 Spathognathodus spinulicostatus spinulicostatus (E. R. Branson) Bischoff : 57, pl. 
4, fig. 27. 
1957 Spathognathodus spinulicostatus spinulicostatus (E. R. Branson) Ziegler in Fliigel 
/ fs) § 8 
& Ziegler: Pl. 1, fig. 14. 
1959 Spathognathodus spinulicostatus spinulicostatus (E. R. Branson) Helms: PI. 3, 
figs. 12a, b. 
1960 Spathognathodus spinulicostatus spinulicostatus (E. R. Branson) Remack-Petitot : 
261, fig. 4. 
1960 Spathognathodus spinulicostatus spinulicostatus (E. R. Branson) Dvorak & Freyer : 
2s tee 6: 
1961 Spathognathodus spinulicostatus spinulicostatus (E. R. Branson) Freyer : 87, 88, Pl. 6, 
fig. 145, text-fig. 146. 
1962 Spathognathodus costatus spinulicostatus (E. R. Branson) Ziegler: 108, Pl. 14, 
figs. 11-18. 
1965 Spathognathodus spinulicostatus spinulicostatus (E. R. Branson) Spasov : 102, Pl. 
By ONES S35 Az 
DERIVATION OF NAME. This is named in honour of Dr. W. Ziegler. 
DiaGnosis. Spathognathodus with subdued oral denticulation. Anterior blade 
deep, but narrowing posteriorly, oral surface being flat. Strong development of 
accessory lateral denticles, up to 13 in number, on outer side of unit. On opposite 
side, posterior end of unit also marked by development of up to 7 smaller lateral 
denticles, giving whole posterior part an asymmetrical platform-like development. 
Basal cavity strongly laterally expanded, but lanceolate in basal outline. 
MATERIAL. Holotype X 403, Paratypes X 402, X 404, X 437 (all figured). 
TYPE LOCALITY AND HORIZON AND RANGE. Ho6nnetal, West Germany to VI Zone— 
Upper costatus Zone, roadside cutting (Ziegler 1962). 
DeEscRIPTION. In lateral view the anterior blade is deep but straight, the oral 
surface bearing a series of reduced even denticles, only the anterior 3 or 4 of which 
have sharply defined apices. There is a tendency for the depth of the anterior blade 
to decrease towards the basal cavity, but the oral edge is straight. Behind the basal 
cavity there is a marked reduction in depth of the unit as seen in lateral view. The 
aboral edge remains more or less straight, but the oral surface slopes down to meet it 
in a relatively straight line. Its oral edge makes an angle of about 160° with the oral 
edge of the blade. The posterior end is spatulate to bluntly-pointed in lateral view. 
The basal cavity is a conspicuous feature when seen in lateral view. The oral 
posterior surface of the unit bears a series of low irregular denticles developed lateral 
to the main blade, but clearly visible in lateral view. These denticles, are developed 
on the inner lateral face of the unit. In outer lateral view the unit is broadly 
similiar. 
In oral view the most striking feature of the unit is the development of up to 13 
