TRANSACTIONS OF THE SECTIONS. 57 
Mr. 8. Wood, jun., admits this division ; “ the upper bed at Norwich,” he says, 
“is the Chillesford shell-bed.” 
Chillesford Crag.—In 1849, Mr. Prestwich made known some marine beds in 
the parishes of Den and Chillesford, either yellow sands or laminated micaceous 
clays. At Iken these beds are superposed upon a worn surface of the older or 
Bryozoan Crag. There is no such direct evidence as to their relation to the Red 
Crag; but there is no doubt that they are unconformable to both divisions. 
These beds are in striking contrast to the true Crag, in respect of their com- 
position and the condition of the shells they contain; they were tranquil depositions, 
the bivalves at every place constantly exhibiting the two shells in contact, and in 
the positions in which the animals had lived. With respect to this fauna, 23 
species only were met with—4 Gasteropods and 19 Acephala. Mr. 8. Wood re- 
cognized the Arctic character of the assemblage, and considered the beds poste- 
rior to the Red Crag, probably the equivalents of the Norwich. The agreement 
with the Bridlington Crag was not very close, there being only six or seven species 
in common, 
Differences of opinion as to detail, both of facts and inferences, might be cited, 
as is well-known to those geologists who have attended to this very complicated 
portion of the geological record ; but thus much seems to have been ascertained, 
that the so-called Chillesford Crag is rather a subordinate member of the marine 
glacial oo than an upper member of the Crag, and that it is referable to a time 
when the climatal conditions, as indicated by the marine mollusca, had undergone 
a great change. 
Bridlington Crag was a name given to a set of marine clay-beds occurring at 
that place, about 30 feet thick; they overlie an accumulation of chalk flints derived 
from the subjacent chalk. 
Mr. 8. Wood, in his Ponogeaph, included these beds in the Crag, and considered 
them the equivalents of the Norwich Crag (1855), 
I am not aware that the fauna of these beds attracted any particular attention 
till Mr. S. P. Woodward prepared his general list of the Norwich-Crag accumula- 
tions for Mr. Gunn’s essay. In 1864 he undertook a fresh examination, not from 
lists, as before, but from original specimens from Mr. Bean’s and Mr. Leckenby’s 
collections ; this led him to the unexpected result that the Bridlington Crag could 
no longer be considered an equivalent of the Norwich Crag. The list of marine 
testacea had been increased to 64 (or by more than 20); of these, 35 are met 
with in the Norwich Crag, whilst 29 species (or one-half) are now living in seas 
north of Britain, the proportion of Arctic shells in the Norwich Crag being only 
one-sixth. 
Mr. Woodward next compared the Bridlington fauna with that of the Clyde 
beds belonging to the close of the “ glacial period,” and with this result, that they 
differed very nearly as much from these as they did from the Norwich assemblage ; 
they must therefore be separated from the Crag series. 
he Bridlington testacea are more indicative of Arctic climatal conditions than 
any assemblage in or about the British Islands. As an assemblage, it is wholly 
recent and living, and marks a stage in the northern submergence during the 
glacial period, when the Arctic-basin marine fauna had extended itself over our 
seas. 
Shells peculiar to Bridlington. 
Fusus gracilis, var. ventricosus, Dentalium Tarentinum (entale). 
Trophon clathratus, Z. (Bamffius). Montacuta bidentata. 
Natica occlusa. Cardita analis? (borealis ?). 
Bowerbankii. Astarte borealis, var. semisulcata, 
Trichotrophis borealis.| Leach. 
Turritella erosa, Couth. (clathratula). mutabilis. 
Margarita elegantissima, Bean. j crebricostata ?. 
Cimoria Noachina. 
The Bridlington beds seem to correspond most nearly in age with those which, 
in Norway, M. Sars has distinguished as his glacial formation. 
Mr. Trimmer candidly admits that, when engaged in the “ Geology of Norfolk” 
