FROM NORTHWESTERN EUROPE 7 
the “‘ Varians Schichten”’ respectively. Both of them are sandy limestones, 
although they differ in that the former contains nodular layers of chert. Each of 
these formations contains an abundance of rhynchonellids and in each of them two 
markedly different types are present. The two rhynchonellids occurring in the 
“Terrain a Chailles” are Septaliphoria arduennensis (Oppel) and Thurmannella 
obtrita (Defrance). The former is much the larger and in having coarse ribs, a strong 
beak and a large pedicle opening was obviously adapted to a high energy environ- 
ment. The much more abundant T. obtrita has relatively much finer ribbing and a 
very thin test, although it too has a well developed pedicle opening. Within the 
“Varians Schichten ”’ the rhynchonellids are of much the same size and occur in 
similar proportions. In this case the larger is Acanthothiris spinosa (Linnaeus) and 
the smaller species is [vanoviella alemanica (Rollier). The former, like S. arduennen- 
sis, tends to occur singly rather than the large groups in which T. obtvita and Ivano- 
viella alemanica are found. The latter species closely resembles T. obtrita externally 
except that it has stronger ribs and a more limited posterior smooth area. It is 
suggested that the similarity of environments in which A. spinosa and S. arduennensis 
are found, and the fact that the latter species is obviously adapted to living an 
attached existence in such conditions is strong evidence for regarding the spines of 
A. spinosa as an anchoring mechanism, especially as its pedicle atrophied during 
ontogeny. This view is in contrast to that of Rudwick (1965) who considered these 
spines to be of a sensory nature. It is thought that the smaller, thinner shelled T. 
obtrita and I. alemanica probably lived attached to algae. This idea is supported by 
the presence of the relatively large pedicle opening, while the very thin shell of T. 
obirita, as seen in silicified material, would appear to preclude its survival on the 
bottom in such numbers in a high energy environment. However, it is always 
possible that they lived in sheltered niches within this environment. 
The same type of environment is suggested for the deposition of the Lower 
Calcareous Grit as seen on the Yorkshire coast. In that area Thurmannella is again 
abundant but any larger rhynchonellids appear to be very much rarer although 
Mr. E. F. Owen (personal communication, 1966) states that he has found Septali- 
phoria on Filey Brigg. The material described below as S. paucicosta sp. nov. came 
from inland localities but it is not known whether or not the species is associated 
with Thurmannella sp. The amount of material in the B.M. (N.H.) would suggest 
that S. paucicosta is very common at least at its type locality of Hutton Bushel. 
The nearest comparable lithology and environment in the Kimmeridgian is pro- 
vided by the Alt-na-Cuile Sandstone of Sutherland. This latter formation is a 
decalcified sandstone containing a rich fauna of rhynchonellids preserved as casts. 
As far as can be determined, given the poor preservation, this seems to be a coarse 
ribbed form closely comparable with Septaliphoria but as its internal structures are 
not preserved its exact relationship cannot be determined. This latter species is 
described below under the name Septaliphoria (?) septentrionalis sp. nov. The 
Abbotsbury Ironstone (Kimmeridgian) of Dorset may also represent this type of 
environment. Here again, the fauna includes poorly preserved rhynchonellids 
doubtfully ascribed to Septaliphoria (?) hudlestoni (Rollier). 
