86 JURASSIC RHYNCHONELLIDS 
Brachial valve. The most important feature is the septalium ; in his original 
description Leidhold (1920) regarded this structure as the diagnostic feature of the 
genus. 
The crural bases are clearly differentiated and are distinctive in that they can be 
seen at the same level as the septalial plates in transverse section. In both the 
species sectioned, the crura ended with the curiously shaped, but consistent, pro- 
cesses seen in text-figs. 31-33. 
Species. The following nominal species are attributed to the genus : 
S. arduennensis (Oppel) (1858, pp. 615, 639, 654) 
2S. hudlestoni (Rollier) (1917, p. 172) 
S. paucicosta sp. nov. 
S. pinguis (Roemer) (pars in Wisniewska 1932, pp. 24-29, pl. I, figs. 1-18) 
2S. septentrionalis sp. n. 
2S. pectunculoides (Etallon) (in Makridin 1964, pp. 102-5, pl. I, figs. 4-6) 
S. sobolevi Makridin (1964, pp. 97-99, pl. I, figs. 16-18). 
DIsTRIBUTION. The taxonomic confusion which has surrounded the genus, 
together with the lack of published serial sections, makes identification from the 
literature very difficult. However, the genus occurs in Yorkshire, northern 
France, the Swiss Jura and ?Dorset. Some of Makridin’s species of Septaliphoria 
from the Russian Platform also undoubtedly belong to the genus, as here defined. 
Remarks. Much confusion has arisen about the exact nature of the genus, 
mainly as a result of two factors. Firstly, Leidhold (1920) chose as his type species 
the poorly defined Rhynchonella arduennensis of Oppel, and secondly, because 
Leidhold’s description of the septalium was based on a misunderstanding regarding 
its development. 
The synonymy of the type species is described under S. avduennensis. A full 
description, with figures and sections of the septalium has already been given in the 
section on morphology and it is only necessary to repeat here that it forms through 
the fusion of the septalial plates with the septum and not as a result of a bifurcation 
of the septum, as originally suggested by Leidhold. 
Septaliphoria arduennensis (Oppel) 
(Pl. 8, figs. 4-5, text-figs. 31-32) 
1858 Rhynchonella Avduennensis Oppel: 615, 639, 654. 
1871 Tevebvatula inconstans Quenstedt: 141, pl. 40, fig. 57. 
1917. Rhynchonella Avduennensis Oppel; Rollier: 171-72. 
1920 Septaliphoria avduennensis (Oppel); Leidhold: 354, pl. 5, fig. 2. 
1932 Septaliphoria avduennensis (Oppel); Wisniewska: 18. 
EMENDED DIAGNOSIS. Medium sized subpentagonal to subtriangular Septali- 
phoria ; biconvex ; frequently slightly asymmetrical ; about 20 simple, subangular 
ribs ; well developed septalium crura radulifer. 
STRATIGRAPHICAL RANGE. Lower Oxfordian ; cordatwm and lower transversariwm 
zones. 
