50 JURASSIC RHYNCHONELLIDS 
ReMARKS. The considerable confusion as to the correct nomenclature of the 
species has largely arisen through the inadequacy of the original descriptions. The 
name obtrita was first used in 1828 by Defrance in the “ Dictionaire des Sciences 
Naturelles ’’; the description was very generalized and while no figure was given, 
he referred to plate 241, fig. 5 in the ‘‘ Encyclopodie Méthodique’’. This latter 
figure is not sufficiently clear for specific identification, although the specimen 
represented certainly belongs within the Thurmannella, Rhynchonelloidella, Ivano- 
viella group. While the specimen figured in the “‘ Encyclopodie ”’ is not named or 
geographically located, in 1820 Schlotheim remarked that it was similar to his 
Terebratulites varians ; this fact is also of interest in that the volume of the “ Ency- 
clopodie ’”’ in which the figure appeared is generally stated to have been published 
in 1827. 
The name Thurmanni first appears in Thirria’s (1833) work “‘ Statistique Minéral- 
ogique et Géologique du Département de la Haute-Saéne ”’, in which the palaeonto- 
logical identifications were given by Voltz. There is no description or figure and the 
name only occurs in the faunal lists for the “‘ argile avec chailles’’ and “‘ marne 
moyenne avec minerai de fer oolithique’’. The first adequate figure of the species is 
by Boyé (1842) in his “ Importance de 1’Etude des Fossiles pour la Reconnaissance 
géologique des Terrains ’’’; again there is no description and the only information 
given is that T. Thurmanmi occurs infrequently in “la marne oxfordienne’”’. Boyé 
placed this between the “ Chailles’’ and the “ Dalle nacrée’’, making it almost 
certainly the “‘ Renggeri Marls’’ of present nomenclature. 
Between 1828 and 1884 the name obtvita does not appear to have occurred in the 
literature, contrasting with thurmanni which was widely used, and the species was 
well figured by several authors under that name. However, in 1884 Deslongchamps 
published a paper in which he redefined the species originally described by Defrance 
(1828), using specimens from the Defrance collection. In this work Deslongchamps 
admitted that the figure in the ‘‘ Encyclopodie’”’ cited by Defrance was not clear 
but went on to say that virtually all the specimens of Defrance labelled as obtrita 
belonged to the form subsequently named thurmanni. Deslongchamps considered 
some of the Defrance specimens to have come from the “ Terrain a Chailles”’ of 
“ Bourgogne or Franche Compté ”’, and not from near Brussels as stated by Defrance, 
while others came from Lons-le-Saunier, Besancon and Méziéres. He then fully 
described the species, i.e. obtvita, and figured three specimens. However, while it is 
assumed that the figured specimens were from the Defrance collection, this is not 
certain as a copy of the original work is not available at the British Museum. It is 
presumed from contemporary synonymies that Deslongchamps produced this paper, 
with its two plates and their explanations, as a separate publication in 1884. 
When the paper on the Defrance species was published in the “ Bulletin de la 
Société linniénne de Normandie ”’ in 1885, for some reason the explanations to the 
plates were omitted. From the remarks of Deslongchamps, there seems little doubt 
as to what Defrance understood by obtrita even though this was not clearly stated in 
his original description. It is presumed that the Defrance collection, which was at 
Caen, was destroyed together with the Deslongchamps collection during the invasion 
of Normandy in 1944. 
