xxii 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. 1 This fauna is a very 

 interesting and important one, but it requires great patience to obtain, 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 Turritetta 

 incrassata, Nassa granulata, Chemnitzia intemodula, Dentalium dentalis, Limopsis pyymcea, 

 Cytherea rudis, Cardita scalaris, C. cordis, Woodia diyitaria, Astarte Burtinii, A. Omalii, 

 and Erycinetta 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 Eluvio-marine Crags 

 and with the Chillesford bed is shown by the presence of Cerithium tricinctum, Tettina 

 obliqua, and Nucula Cobboldics — 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. 2 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. 



5 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. 



