BRITISH AVONIAN CONODONT FAUNAS 181 
Genus PLECTOSPATHODUS Branson & Mehl 1933 
1933 LPlectospathodus Branson & Mehl : 47. 
TyPE SPECIES. Plectospathodus flexuosus Branson & Mehl. 
Plectospathodus ? sp. nov. A 
Plate 25, figs. 8a—9 
MATERIAL. 3 specimens : figured, X 312, X 313. 
RANGE. North Crop ZLA 33. 
Description. A plectospathodid characterized by a long anterior bar ; denticles 
free standing, sub-circular in cross-section and posteriorly inclined ; those in the 
median third the largest. Apical denticle larger than bar denticles, ovate in cross- 
section, and posteriorly and laterally inclined. Posterior bar about equal in length 
to anterior bar, twisted and with slight inward curvature, the posterior tip down- 
flexed. Denticles small, fine, except for terminal denticle, which is as large as apical 
denticle, and may have small denticles developed on its posterior face. 
The basal cavity is open, flared on the inner side, with a “ nick’ in the inner lip 
beneath the apical denticle ; it extends beneath the posterior and anterior bars for a 
short distance. 
REMARKS. The genus Plectospathodus has previously been described only from 
rocks of Upper Silurian and Lower Devonian age, but these specimens agree perfectly 
with the generic description given by Branson & Mehl (1933A : 47). 
Plectospathodus ? sp. nov. B 
Plate 25, figs. 10-12 
MATERIAL. 4 specimens : figured, X 427, X 428, X 314. 
RANGE. North Crop 3D 14/15-3D ro. 
DESCRIPTION. Very small units consisting of two bars, roundly arched at their 
junction. Oral edges denticulate. A conspicuous apical denticle. Denticles of 
Apical denticle 
Terminal denticle 
A“ 
nam 
Fic. 36. Plectospathodus sp. showing morphological terms used in the text. 
Anterior bar ~ Posterior bor 
Basal cavity 
