XX SUPPLEMENT TO THE CRAG MOLLUSCA. 
contorted drift at Blaxhall, and Kesgrave, lie just within the limits of the Red Crag area. 
The foregoing figure shows the manner in which these Middle Glacial sands along the 
Deben region rest on and envelope rugged surfaces of the Red Crag. 
Over the greater part of their range these sands are unfossiliferous, and it is only in 
the neighbourhood of Yarmouth that they have yielded a fauna.’ ‘This fauna is a very 
interesting and important one, but it requires great patience to obtam, owing to the sparse 
occurrence and fragmentary condition of the specimens. ‘The two principal places from which 
it has been procured, are Billockby, eight miles north-west of Yarmouth, and Hopton Cliff. 
At the latter place (see Section U) the sands are underlain by the contorted drift, No. 7, 
and overlain by the chalky clay, No. 9. At Billockby they are overlain by the clay 
No. 9, while No. 7 comes out along the lower ground. No question can thus arise as 
to the position of the sands from which this fauna has been obtained, The specimens 
come from a thin shelly seam at the top of the formation some four or five feet below the 
clay, No. 9. ‘This fauna is specially interesting, not only as showing a much older aspect 
than that of any of the Glacial beds of Scotland, and even of Bridlington, but also in its 
approaching that of the Coralline Crag by the presence of such species as Turritella 
éncrassata, Nassa granulata, Chemuitzia internodula, Dentalium dentalis, Limopsis pygmed, 
Cytherea rudis, Cardita scalaris, C. corbis, Woodia digitaria, Astarte Burtinui, A. Omalii, 
aud Hrycinella ovalis, the three last of which are not known living, Cardita scalaris 
being a Pacific shell, and the rest Mediterranean and Atlantic species, not ranging so far 
north as Britain. On the other hand, its affinity with the Red and Fluvio-marine Crags 
and with the Chillesford bed is shown by the presence of Cerethium tricinctum, Tellina 
obliqua, and Nucula Cobboldie—species not known as living—as well as by that of several 
other Red Crag forms which are now living in the Mediterranean and range into British 
seas, but which are unknown further north.? In this respect the Middle Glacial fauna 
presents a contrast (which no difference of latitude will explain) not merely to the Post- 
glacial beds of Kelsea, March, Hunstanton, and the Nar valley, but also to the fossiliferous 
so-called Glacial beds of the Severn valley, of Wales, of the North-west of England, and 
of Scotland. Messrs. Crosskey and Robertson, to whom some of the sand was submitted, 
found on a cursory examination that the Foraminifera occurring in it were, like the shells, 
much worn, and that they presented an arctic character, varied by the presence of one or 
two Tertiary forms. The peculiarity of this fauna naturally prompts a suspicion that it 
may be derivative from the Crag, and it is necessary therefore to examine that question. 
1 We have observed fragments of shells in the Middle Glacial, however, at other places, viz. at Wisset, 
two miles north-west of Halesworth; at the Brick kiln on the North of Stowmarket (where the sand is 
overlain by a Post-glacial Brick clay) ; and at Helmingstone, six miles north of Ipswich. 
? This Fauna, as well as that of the Lower Glacial, will be given by the author of the ‘Crag Mollusca ’ 
in the tabular list to appear in the concluding part of his ‘Supplement.’ In the meantime see, as to the 
Middle Glacial Fauna (latest results), ‘Geol. Mag.’ vol. viii, p. 410; and as to the Lower Glacial Fauna, 
‘Quart. Journ. Geol. Soc.,’ vol. xxvi, p. 92. 
