BRITISH AVONIAN CONODONT FAUNAS 153 
The denticles form a fused series of bluntly pointed confluent denticles, about 5 or 
6 in number, grading in the antero-aboral region into minute and inconspicuous 
confluent denticles. The antero-aboral portion is flexed sharply outwards ; the 
posterior denticle is inclined slightly posteriorly. The whole posterior outer lateral 
face of the platform slopes gently inwards to meet the basal slit, giving a boat-like 
appearance to the unit in lateral view. It is convex to flat in its upper part and may 
become concave in its postero-aboral portion. In inner lateral view the same feature 
is seen. The platform is relatively straight in its posterior third, but is regularly 
concave in its anterior third or half. The inner lateral margin is generally developed 
at a lower level than the outer lateral margin, and is finely denticulated, the inner 
anterior edge of the platform bearing rather conspicuous low denticles. The antero- 
aboral inner edge is strongly convex and is deflected inwards. It is much less deep 
than the corresponding outer aboral anterior edge. 
Mestognathus neddensis sp. nov. 
Plate 15, figs. 4a—6c 
DERIVATION OF NAME. From the River Nedd, Breconshire. 
DiacGnosis. Mestognathid with short deep anterior blade, bearing 6 denticles, 
those at anterior end being only slightly shorter than those at posterior ; their apices 
are discrete. Anterior blade and inner anterior edge of platform bifurcate at the 
anterior end of the unit. Posterior platform straight on outer lateral side and gently 
convex on inner lateral side, posterior inner lateral portion being strongly pinched 
inwards towards pointed posterior end. Strong posterior carina, consisting of low 
rounded nodes along posterior half of platform, becoming obsolescent towards 
anterior inner lateral edge of platform. 
MATERIAL. 5 specimens : Holotype X 250, Paratypes X 251, X 252 (all figured). 
TYPE LOCALITY AND HORIZON. North Crop. Sample CYD 6. 
Rance. North Crop CYD 6-CYD 7. 
DeEscriPTION. In oral view the unit is elongated and slender. The anterior blade 
is free for only a very small portion of its length, but the anterior end of the platform 
is marked by a V-shaped indentation, formed by the junction of the anterior blade 
and the inner anterior margin of the platform. The blade is conspicuously denticu- 
lated in oral view and the outer lateral margin of the platform is more or less straight. 
It is ornamented by a series of transverse denticles which are more strongly developed 
in the anterior portion than the posterior. The inner lateral platform is gently 
sinuous, being straight to gently concave in the anterior third and strongly convex in 
the posterior two thirds. The posterior carina extends beyond the posterior limit 
of the platform, so the whole appearance of the platform is rather pinched posteriorly. 
The inner lateral margin of the platform is ornamented by feeble, nodular to trans- 
verse ridges which become obsolescent towards the anterior part. The posterior 
half of the platform is marked by a conspicuous carina, consisting of 7 or 8 low 
rounded fused nodes, and is extended as a rather inconspicuous ridge towards the 
