BRITISH AVONIAN CONODONT FAUNAS 
to 
N 
fo.) 
Spathognathodus costatus sulciferus (Branson & Mehl) 
Plate 3, figs. 16a—18c 
1934 Spathodus sulciferus Branson & Mehl: 274, Pl. 22, figs. 12, 13. 
1934 Spathodus spinulicostatus E. R. Branson : 305, Pl. 27, fig. 19. 
1938 Spathodus spinulicostatus E. R. Branson ; Branson & Mehl: 132, Pl. 33, fig. 2. 
non 1939 Spathodus sulciferus Branson & Mehl ; Cooper : 416, Pl. 45, figs. 17, 18 (fig. 17 = S. 
cyrius, fig. 18 = S. crassidentatus). 
1944 Spathodus spinulicostatus E. R. Branson ; E. B. Branson Pl. 32, fig. 2. 
1944 Spathognathodus sulcifeyus (Branson & Mehl) Branson & Mehl in Shimer & Shrock : 
Pivo4, figs2. 
? 1961 Spathognathodus costatus spinulicostatus (E. R. Branson) Higgins, Wagner-Gentis & 
Wagner: Pl. 5, fig. 22. 
MATERIAL. 29 specimens : figured, X 457, X 458, X 459. 
RANGE. North Crop ZLA 4-ZL 10, Avon Gorge K 18-Z 26. 
DeEscRIPTION. The unit is straight, very slightly arched and highest at the 
anterior end. The anterior blade consists of 3 to 4 high denticles, its oral outline 
being gently convex upward. The medial part of the unit possesses denticles of 
equal height, the posterior part having denticles which become progressively lower 
toward the posterior termination. Both lateral faces of the unit bear nodes, the 
inner row of about Io being similar to the inner row of S. costatus costatus, with the 
largest nodes lying in the medial position and having depressed and inconspicuous 
transverse connecting ridges. The outer lateral dentition is confined mainly to the 
area of the oral side of the cavity lip and consists of 1 to 3 large fused nodes of lower 
height than the inner row. The posterior part of the outer face occasionally bears 
isolated denticles (Pl. 3, fig. 16). 
In aboral view the cavity is large, medial and sub-symmetrical, tending to have a 
greater amount of flaring on the outer side ; it is about twice as long as wide and runs 
posteriorly as a narrow groove. It is laterally expanded, and wider at the anterior 
end. 
ReMARKS. S. costatus sulciferus is obviously very closely related to S. costatus 
costatus, differing only in the addition of lateral denticles on the outer side. Further 
enlargement of the outer platform gives species referable to the genus Pseudopoly- 
gnathus, although that genus is polyphyletic. 
Spathognathodus crassidentatus (Branson & Mehl) 
Plate 3, figs. Ia—4b 
1934 Spathodus crassidentatus Branson & Mehl : 276, Pl. 22, figs. 17, 18. 
1934 Spathodus crassidentatus Branson & Mehl; E. R. Branson : 303, Pl. 27, fig. 12. 
1934 Spathodus denticulatus E. R. Branson : 305, Pl. 27, fig. 17. 
1934 Spathodus aciedentatus E. R. Branson : 306, Pl. 27, figs. 21, 23. 
1934 Spathodus strigilis Huddle : 89, Pl. 7, fig. 15 ; Pl. 12, fig. rz. 
1934 Spathodus parvus Huddle : go, Pl. 7, fig. 16. 
1938 Spathodus crassidentatus Branson & Mehl ; Branson & Mehl: 132, 137, Pl. 33, fig. 5. 
1938 Spathodus elongatus Branson & Mehl (partim) : 139, Pl. 34, fig. 9 (non Pl. 34, fig. 6 = S. 
elongatus). 
