ON RHYNCHONELLA ACUTA AND ITS AFFINITIES, 5 
Yorkshire, it appears to me that the author has merely represented 
more aged examples of the two varieties before us as species distinct 
from the first named. 
Professor Morris, in the last edition of his “ Catalogue of British 
Fossils,” treats the difference of a plication, more or less, between 
R. bidens and R&R. triplicata as unimportant, although, instead of 
uniting these to R. acuta, and assigning to the three forms one specific 
name, he records them as synonyms of R. variabilis, one of the most 
widely-diffused brachiopods of the Lower Lias, and of which I doubt 
the occurrence in the marlstone of England at least. 
In certain localities, as at Frocester, a young or dwarfed form of 
Ki. tetrahedra constitutes the principal bulk of large masses of marl- 
stone, and has, I think, been mistaken for R. variabilis ; but in neither 
of these species can I discover any features at all suggestive of affinity 
with that under consideration. That Professor Morris may be mis- 
taken is not improbable, from the fact that the two most recent writers. 
on the Jurassic formations of England and the continent, Oppel and 
Quenstedt, have both found themselves somewhat perplexed as to 
the true affinities of these forms, perhaps, to some extent; in conse- 
quence of having adopted, without due examination, his views. 
Oppel, in his observations on R. variabilis (“ Juraformation,” p. 187), 
after stating that it is found in the Middle as well as the Lower Lias, 
remarks, pertinently enough as regards the object of the present 
paper, that, “in Suabia it occurs particularly under the form of the 
biplicated variety (R. bidens of Phillips), which is found also at the 
base of the Middle Lias at Boll, Metzigen, Hinterweiler, and Balingen, 
with specimens possessing a greater nwmber of folds (R. variabilis of 
Zieten, p. 42, f. 6, and R. triplicata of Phillips). 
Bearing in mind the fact that R. variabilis of Zieten is not the 
typical form recognized by Schlotheim or Davidson, it. is clear that 
Dr. Oppel considers the forms just described as belonging to one 
species, and, in his observations on R. variabilis of the Lower Lias 
(p. 121), he appears disposed to limit its stratigraphical range to the 
Lower Lias only, in which case, of course, they are not varieties of . 
the latter. 
Professor Quenstedt, in like manner, in his recently-published 
“ Jura,” treating of BR. bidens, Phillips, seems disposed to consider it 
and I. triplicata as varieties of R. acuta, distinctly pointing out their 
