222 BRITISH AVONIAN CONODONT FAUNAS 
1959 Ctenognathodus nom. nov. Fay : 195 (pro Ctenognathus Pander 1856). 
1959 Ctenognathus (Ctenognathodus) Fay : 195. 
1959 Ctenognathodus (Mehlina) Fay 195. 
1962 Spathognathodus (Bispathodus) Miller : 114. 
TYPE SPECIES. Ctenognathus murchisom Pander 1856. 
The name Pandorinellina was first used by Miller & Miller (1957 : 1083) but was 
clearly attributed by them to Hass in the (then forthcoming) Treatise. Article 50 
of the Code of Zoological Nomenclature justifies the attribution of the genus to Hass. 
Spathognathodus anteposicornis Scott 
Plate 3, figs. 5a—8b 
1961 Spathognathodus n. sp. A Scott & Collinson : 132, Pl. 1, figs. 12-15. 
1961 Spathognathodus anteposicornis Scott : 1224, text-fig. 2H — K. 
MATERIAL. 59 specimens : figured, X 540, X 541, X 542, X 543. 
RanGE. North Crop KL 19-ZLA 15, Avon Gorge Kg 1-Z 28. 
DescriPTion. The unit is elongate, being two to three times as long as the 
highest anterior denticles ; it is straight in oral view, and highest at the anterior. 
The anterior 3 denticles are the largest, standing twice as high as the remaining blade 
denticles, the medial denticle of the three usually being highest. The remaining 
denticles are of equal height over the medial third, gradually decreasing in size 
posteriorly over the posterior third ; they are erect, basally fused and blunt tipped. 
The aboral edge is straight (Pl. 3, fig. 5a) to gently arched (PI. 3, fig. 7a). A lateral 
denticle, sub-circular in cross-section, is developed high on the inner side of the unit 
over the anterior portion of, or immediately anterior to, the basal cavity, the tip 
generally being about equal in height to the adjacent denticles of the blade. 
In aboral view the basal cavity is large and flaring, with an anterior pit. The 
cavity occupies the median third and extends in both directions as an aboral groove. 
The outer margin of the cavity is subcircular (PI. 3, fig. 5b) to biconvex (PI. 3, fig. 6b). 
REMARKS. Scott (1961 : 1224) described this species from the Louisiana Lime- 
stone, which he regarded as Upper Devonian. Our specimens, which have a 
restricted range above the Avonian occurrence of the genus Szphonodella, would 
appear to be stratigraphically younger. Their occurrence in the present faunas may 
be the result of one or more of at least three different factors : an independent 
phylogenetic origin, so that they are homoeomorphs of Scott’s S. anteposicornis : a 
greater stratigraphic range for that species than has been hitherto supposed : or a 
Lower Carboniferous age for the Louisiana Limestone. Without firm evidence in 
support of any one interpretation, it seems preferable to assign the present specimens 
to S. anteposicornis Scott. 
One feature of the stratigraphically older specimens of this species (PI. 3, fig. 6a), is 
the prominent square antero-aboral angle of the blade, and the posterior inclination 
of the three large anterior denticles. These features, though present, are less marked 
in stratigraphically younger specimens (e.g. Pl. 3, fig. 7a). There also seems to be an 
