FROM NORTHWESTERN EUROPE 51 
Since the Deslongchamps paper, most authors, with the notable exception of Haas 
(1889), have continued to use the name thurmanm. Rollier (1917) suggested that 
the name obtrita should be abandoned and at the same time proposed the restriction 
of the name thurmanni to the smaller forms as typified by the material from the 
renggert Marl. He placed the larger specimens coming from the “ Terrain a 
Chailles ’’ in a new species stlicola. To the present author, this arbitrary division 
seems to have little justification, apart from being inadmissible on the grounds of 
priority. 
In setting up his new subgenus Thurmannella, Leidhold (1920) included only two 
species, namely 7. obtrita and T. thurmanm, nominating neither as type of the genus. 
These two ‘ species ’ were differentiated on the grounds that the valves of T. obtrita 
were less inflated and that the uniplication was less developed than in T. thurmanni ; 
however, as they occur together at the same horizon and localities and as the features 
mentioned above show complete gradation between the ‘end members ’, it is here 
considered that Leidhold was in fact dealing with one species. The synonymy given 
by Leidhold for his two species is interesting in that he placed T. thurmanni of Boyé 
in synonymy with T. obtrita of Defrance, so separating it from T. thurmanni of 
Voltz ; the grounds on which this decision was made are not made clear. 
It is concluded that the name obtvita of Defrance has priority over thurmanni of 
Voltz and that 7. obtrita should be regarded as the type species of Thurmannella. 
Thurmannella acuticosta sp. n. 
(Pl. 5, figs. 10-11, text-fig. 20) 
1878 Rhynchonella varians var. Thurmanmi (Voltz); Davidson: 215-16, pl. 28, figs. 14-16. 
1933 Rhynchonelloidea thurmanni Arkell: 432. 
Name. Latin, acutus-a-um—sharp, pointed ; costa-ae—a rib ; the species has 
very sharp ribs. 
Diacnosis. Medium sized Thurmannella ; about 17-18 relatively coarse, steep, 
subangular ribs ; possesses only very limited posterior smooth area ; crura cal- 
carifer. 
STRATIGRAPHICAL RANGE. Lower Oxfordian—mariae zone and lower cordatum 
zones. 
TYPE SPECIMEN. Holotype selected is the specimen figured Davidson (1878) pl. 
28, fig. 16. 
DIMENSIONS OF HOLOTYPE. Length 1-61 cm, thickness 1:46 cm, width 1-74 cm. 
DESCRIPTION. External characters. The shell outline is subpentagonal to 
weakly trilobate, the latter condition resulting from the very strongly developed 
uniplication shown by some specimens. The uniplication in the anterior commissure 
is emphasized by the strong, steep nature of the subangular ribs. No concentric 
ornament has been observed. 
The beak is sharp and suberect to erect ; the erect condition is much less common 
than in T. obtrita and, in comparison with that species, the interarea is smaller and 
less incurved. An oval, submesothyridid pedicle opening is present ; the details of 
