BRITISH AVONIAN CONODONT FAUNAS 183 
1957 Polygnathus communis Branson & Mehl ; Bischoff : 42, Pl. 2, figs. 23-27. 
1957 Polygnathus communis Branson & Mehl; Ziegler in Fliigel & Ziegler: 46, Pl. 2, 
fig. 15. 
1959 Polygnathus communis Branson & Mehl ; Hass: 390, Pl. 49, figs. 9-11, 13. 
1959 Polygnathus communis Branson & Mehl; Helms: PI. 3, fig. 11. 
1959 Polygnathus communis Branson & Mehl ; Voges: 288, Pl. 34, figs. 1-7. 
1960 Polygnathus communis Branson & Mehl ; Ziegler: PI. 1, fig. 9. 
1960 Polygnathus communis Branson & Mehl ; Dvorak & Freyer : 884-888, Pl. 1, figs. 15, 
16. 
1960 Polygnathus decorosa Stauffer ; Dvorak & Freyer : 882, Pl. 2, figs. 1-2. 
1961 Polygnathus communis Branson & Mehl ; Beach : 49, Pl. 6, figs. 1-4. 
1961 Polygnathus communis Branson & Mehl ; Scott & Collinson : 130, Pl. 1, figs. 6-10 
Pl. 2, fig. 30. 
1961 Polygnathus communis Branson & Mehl ; Freyer : 7o. 
1962 Polygnathus pura Voges; Miiller : 1388, text-fig. 2a, b. 
1964 Polygnathus communis communis Branson & Mehl; Rexroad & Scott: 33, Pl. 2, 
figs. 17, 18. 
1964 Polygnathus communis Branson & Mehl; Higgins, Wagner-Gentis & Wagner : 225, 
Pl. 5, fig. 30. 
1964 Polygnathus communis Branson & Mehl ; Budurov & Tschurner: PI. V, figs. 1a, b, 
Za, b, £2, 18: 
1965 Polygnathus communis Branson & Mehl ; Spasov : 95, Pl. 2, figs. 15, 15a. 
1965? Polygnathus communis Ethington : 581, Pl. 67, fig. 7. 
MATERIAL. 740 specimens : figured, X 346, X 347, X 348. 
Rance. North Crop KL 3-ZL 10, Avon Gorge K 3-C 9. 
Description. The platform varies in shape from ovate to lanceolate, but is 
unornamented except for a medial nodose carina. The platform edges tend to be 
upturned and thickened. The anterior blade varies in length but is commonly equal 
to the platform length, bearing from Io to 16 laterally compressed, fused denticles ; 
the oral outline of the blade is convex. 
In aboral view the cavity is fairly large, circular, and situated at the junction of the 
platform and the anterior blade. Insome specimens the cavity appears on the blade. 
The aboral surface of the unit posterior to the cavity tends to be concave. The 
cavity is extended as a tapering slit along the anterior blade, to a point just anterior 
to its mid point. A keel runs from the margin of the main cavity to the posterior tip 
of the platform ; its aboral surface may bear a fine groove. The aboral surface 
makes a sharp obtuse angle with the lateral faces of the outer platform margins, 
giving a chine-like aboral appearance to the unit. 
REMARKS. Carinate and bifurcate subspecies of Polygnathus communis known 
from America are not present in our fauna, but the species is very variable throughout 
the section. A single specimen (Pl. 12, 1a—c) is obviously close to individual speci- 
mens assigned to this species, but differs in the general form of the oral surface of the 
platform. The anterior lateral margins of the platform are strongly constricted and 
upturned, giving almost a Siphonodella-like appearance to the anterior portion. The 
posterior portion is wide, shallow and bluntly rounded posteriorly, the whole having 
the general appearance of a shallow spoon. There is no ornamentation and the 
carina continues as a series of distinct blunted nodes to the posterior end of the 
