BRITISH AVONIAN CONODONT FAUNAS 231 
Diacnosis. Spathognathodid with plume-like anterior blade, having one node 
developed on outer lateral face above basal cavity. 
MATERIAL. 10 specimens : Holotype X 384, Paratype X 385 (both figured). 
TYPE LOCALITY AND HORIZON. R. Clydach, Nr. Gilwern, Lower K Zone North 
Crop. Sample KL 2. 
RANGE. North Crop KL 2-KL 3, Avon Gorge K 4-K 8. 
DescripTION. The blade is short and thin, the anterior part consisting of a 
posterior high, massive, recurved, laterally compressed denticle, and the denticles 
rapidly decreasing in height anteriorly, to give a plume-like effect. The medial and 
posterior parts of the unit consist of low, fused, laterally compressed, erect to slightly 
posteriorly inclined denticles. Above the anterior part of the outer cavity lip, a 
single lateral node denticle arises, which is sub-circular in cross-section. 
In aboral view the cavity is elliptical, slightly flared and its long axis is concordant 
with the long axis of the unit. 
REMARKS. This form appears to occupy the same position within the S. plumulus 
lineage as does S. anteposicornis Rexroad & Scott within the S. trvidentatus lineage. 
The small size of all the present specimens might be interpreted to mean that they 
are a growth stage of S. plumulus plumulus sp. nov., but the presence of three 
denticles in specimens of that species of comparable small size (Pl. 1, fig. 6) and the 
restricted range of the present subspecies appear to justify its recognition as distinct. 
Spathognathodus pulcher (Branson & Mehl) 
Plate 4, figs. ga—1Ic 
1938 Spathodus pulchey Branson & Mehl: 139, Pl. 34, figs. 7, 8. 
MATERIAL. 59 specimens : figured, X 386, X 512, X 513. 
Rance. North Crop KL 19-ZLA 15, Avon Gorge Z 12-C 7. 
DescripTion. The blade is long and thin, being highest at the anterior and 
decreasing gradually to a point anterior to the basal cavity, where the profile becomes 
straight, sloping off abruptly at the posterior termination. The 14 to 15 sub-circular 
denticles are erect, short, fused at the bases, and free at the sharply pointed tips. 
The cavity is elongate, expanded, and occurs in the posterior half of the unit, 
terminating immediately anterior to the posterior end. The anterior part of the 
blade is about twice as deep as the posterior. 
REMARKS. This form differs from S. cvassidentatus s.s., in the lack of a distinct 
high blade at the anterior end, and in the posterior (rather than medial) position of 
the basal cavity. It resembles S. elongatus in the anterior half, but the sudden 
termination immediately posterior to the basal cavity is distinctive (Branson & Mehl 
1938A : 139-140, Pl. 34, figs. 7,8). Itis very similar to a form described by Branson 
& Mehl (1938A) as S. elongatus (PI. 34, fig. 9) which was referred by Cooper (1939) toa 
new species, S. chouteauensis. Rexroad & Scott (1964) refer this to S. crassidentatus, 
but it would appear not to fit even their broad terms for the species. The present 
specimens are also close to S. stabilis. 
