28 SUPPLEMENT TO THE CRAG MOLLUSCA. 
correct. The peculiar ornamentation of the upper volutions is spoken of in the “ Brit. 
Moll.,’ as also in ‘ Brit. Conch.,’ but it has never been represented. 
TROPHON MuRIcaTUS. Crag Moll., vol. i, Tab. VI, fig. 5. 
A perfect specimen has occurred in the Middle Glacial sand of Billockby, but I have 
not met with it from the Fluvio-marine Crag, the Chillesford bed, or from the Lower 
Glacial sands. 
Tropuon MEDIGLACIALIS, S. Wood. Supplement, Tab. VII, fig. 12, a, 6. 
Spec. Char. T. Testa elongato-fusiformi, anfractibus rotundatis, longitudinaliter 
costatd, costis (8—10) elevatis obtusis ; spiraliter lineata, lineis paucis elevatis ; apertura 
ovata ; cauda elongata. 
Locality. Middle Glacial, Billockby, and Hopton. 
Length, half an inch nearly. 
About a dozen specimens of this shell have occurred in the Middle Glacial sand of. 
Billockby, and five in that of Hoptcn, and as they do not vary greatly in size, I infer 
that the specimen figured is a full-grown shell, or nearly so. Like almost all the fossils 
from this formation, the specimens are im a more or less injured condition ; but the one 
figured has suffered but little, as the spiral strize are preserved on it. ‘The upper part of 
the whorls do not show any spiral striation, and this appears, not only in the specimen 
figured, but on such others as retain the external markings. As all the specmens, however, 
are more or less worn, this absence of striata on the upper part of the whorl may possibly 
be due to erosion. The costs appear to be nearly equal in number on all the volutions. 
None of the specimens indicate any less tapering form than that figured, while some are 
slightly more tapering and slender. 
This species being unknown to me from any other formation than the Middle Glacial 
sand of Hast Anglia, while it is somewhat numerous there, it appears to be characteristic 
of that formation; I have therefore assigned to it the specific name of mediglacialis. 
TRopHon ? Britocksrensis, S. Wood. Supplement, Tab. VII, fig. 13. 
Locality. Middle Glacial, Billockby. 
Length, % of an inch. . 
A unique specimen in good preservation from Billockby, shown in fig. 13, is the 
foundation for this species, but whether it be a young specimen or a full-grown shell, 
there are no means of judging. It differs from medig/acialis in its less tapering form, 
