188 BRITISH AVONIAN CONODONT FAUNAS 
TYPE LOCALITY AND HORIZON. North Crop. Sample KL 19. 
RANGE. North Crop KL 17-KL 19, Avon Gorge K 17. 
REMARKS. As was noted by Rexroad & Scott (1964) P. longiposticus belongs to 
the P. inornatus group of polygnathids. It can be distinguished from P. znornatus 
s.s., by the lanceolate platform and the longer free blade. The present subspecies 
approaches P. longiposticus in these respects. 
Polygnathus lacinatus Huddle 
Certain polygnathids with a lanceolate platform and an elongate, excavated cavity 
were referred to a new species, P. lacinatus, by Huddle (1934). This species was 
recognized by Cooper (1939), but Youngquist with various co-authors (Youngquist & 
Patterson 1949, Youngquist, Miller & Downs 1950, and Youngquist & Downs 1951), 
referred similar forms to P, sagittarius Youngquist & Patterson. German workers, 
describing collections from condensed sequences of strata, included P. lacinatus 
within the species P. inornatus E. R. Branson, thus extending both the stratigraphic 
range and concept of that species. The distinctive feature of P. lacinatus is the 
marked longitudinal extension of the rim of the basal cavity, which is often half the 
total platform length (e.g. Pl. 11, fig. gb). 
P. lacinatus appears to us to be a valid species. It is restricted to an interval 
comparable with beds of Cu II 8/ age in Europe. Its generic affinities are somewhat 
doubtful. Huddle stated that the platform was a perfect polygnathid platform, 
although the basal cavity differs markedly from the “ typical” cavity of that genus. 
The possession of a large basal cavity brings it within the morphological scope of the 
genus Pseudopolygnathus, but the lack of asymmetry of the cavity and the poly- 
gnathid nature of the platform lead us to conclude, like Huddle, that this form is a 
polygnathid. Later phylogenetic work may show that this is not the case. Within 
our faunas there appear to be several variants, and these have been referred to new 
subspecies. Forms referred to P. lacinatus lobatus show lobation of the posterior 
part of the outer platform, and considerable narrowing of the anterior part of the 
platform, with upturning of the platform edges. This tends to give these specimens 
an overall siphonodellid appearance, but the basal cavity and lack of rostral ridges 
set them apart from the genus Szphonodella. 
Polygnathus lacinatus asymmetricus subsp. nov. 
Plate 11, figs. Ia—4c 
DERIVATION OF NAME. From the asymmetrical development of the platform. 
DiaGcnosis. Subspecies of P. lacinatus with reduced inner platform, giving 
asymmetrical platform outline. 
MATERIAL. 295 specimens : Holotype X 361, Paratypes X 360, X 362, X 363 
(all figured). 
TYPE LOCALITY AND HORIZON. North Crop. Sample ZLA 32. 
