FROM NORTHWESTERN EUROPE 87 
TYPE SPECIMEN. A neotype is here proposed in view of the uncertainty which has 
surrounded this important species. Although the specimen chosen is not from any 
of the localities cited by Oppel (1858) it is from the horizon mentioned by him, 
namely the “‘ Terrain a Chailles ’’, and has been selected to conform as nearly as 
possible to the specimen figured by Leidhold, as he was the first to figure the species 
as such and, consequently, his figure has been accepted as definitive both of the 
species and of the genus Septaliphoria of which it is the type. Unfortunately, it is 
not possible to collect material from the area around Méziéres mentioned by Leidhold, 
as the Oxfordian is no longer exposed there (Dr. Maubeurge, personal communication 
1965). As the specimen figured by Leidhold shows the internal structure, it seems 
probable that it was a silicified specimen from the “ Terrain a Chailles ”’. 
The author has not been able to find the type specimens of either Oppel or Leidhold 
and it is considered highly unlikely that they still exist in a recognizable form. The 
neotype was collected from the “ Terrain a Chailles”’ at Pagny-sur-Meuse, near 
Nancy, France. 
DIMENSIONS OF NEOTYPE. Length 2:33 cm; thickness I-90 cm and width 
2°60 cm. 
MATERIAL. 25 specimens from Pagny-sur-Meuse (Meurthe et Moselle), including 
BB.44173, BB.44174. 
DeEscrRIPTION. External characters. The outline of adult specimens is sub- 
pentagonal while that of the smaller ones is subtriangular ; the smaller specimens 
also tend to be equally biconvex while the larger ones have a more inflated brachial 
valve. 
The beak is suberect and flanked by fairly well developed beak ridges. The inter- 
area is relatively large and either flattened or slightly incurved. The deltidial plates 
are either disjunct or just conjunct. A large, well developed, circular pedicle 
opening is present and was presumably functional at all stages. Concentric orna- 
ment appears to be restricted to occasional, poorly developed growth lamellae. 
DIMENSIONS OF FIGURED SPECIMENS. 
length thickness width 
2°49 cm I-73.cm 2-07 cm 
2°33 cm I-90 cm 2:60 cm 
Internal characters. All the specimens available were silicified and much of the 
fine detail of the internal structure has been lost. 
Pedicle valve. The narrow, elongated lateral cavities are delimited by slender, 
ventrally divergent dental lamellae which break away from the ventral wall of the 
valve well to the posterior of the plane of articulation. The teeth are strong and 
crenulated ; lateral denticulae are present. 
Brachial valve. A septalium is present and can be clearly seen in text-fig. 32. 
It is less distinct in the other specimen sectioned, probably as a result of partial 
silicification. The crural bases are distinct and can be seen lying immediately 
behind the septalial plates in section 1, 5 of text-fig. 31 ; the crura are of the radulifer 
type. The hinge apparatus is strong with crenulated sockets and both inner and 
outer socket ridges well developed. 
