Alfred Bell-^The Succession of the Crags. 213 



glaciale, Nassa consociata^ N. elegans, N, prismatica, Desmoulea con- 

 globata, Pleur. carinata, P. decussata, etc., Natica cirriformis, N. 

 varians, Scalaria fimhriosa, Adeorbis subcarinatus, Emargimda crassa, 

 BroccTiia partim-sinuosa, Scaphander lignarius ; that is to say, 37 

 species of one pit unrepresented in another pit close at hand. If the 

 peculiar contents of pit G are examined, we find amongst them 

 BJiynchonella psittacea, Buccinum ciliatum, Pleurotoma exarata, Fusus 

 Largillierti, F. Turtonis, Natica nitida, N. occlusa, N. Groenlandica, etc. 

 Many other forms in this pit are very rarely represented, to what 

 they are in the other places, and vice versa; thus, while in the majority 

 of the old pits (D. etc.) the sinistral form of F. antiquus is the pre- 

 dominant one, in the newer horizon, it is the dextral forms that 

 most abound. There are many other differences in size and arrange* 

 ment of the fossils, that I need not stop to go into. I think I have 

 shown sufficient reason against the argument that the two faunas 

 were deposited in the same sea. Of the peculiar shells of the older 

 beds, Waldringfield alone would supply 40, and Walton 20 more, in 

 addition to the above. 



The juxtaposition of the Eed Crag in pits T) and G to the Coralline 

 Crag Cliff, is available upon another point. If the Ked Crag fauna is 

 so largely supplemented by Coralline Crag fossils, how comes it that 

 here the Coralline Crag fauna is so sparely represented. Where are 

 the Limce, sm.allAstartes, Verticordice, Poromyce, Panopece {P.fragilis), 

 Tellina donacina, or the many CJiemnitzice, Eulimce, Odostomice, 

 Pyramidellce, Triforis, Cerithia, and CeritMopses, Cceca, DiscMdes, 

 all the Opisthobranchs, and many other genera ? I cannot find them 

 in the ordinary way a collector works, i.e. by careful sifting of the 

 material in which they ought to be found, and I confess that except 

 the wear and tear of the sea in rolling the broken-up Crag had, as 

 I suspect it has, totally destroyed its contents, I am at a loss to 

 explain their absence. It is certain that they are not there. 



Concerning the depth of the Eed Crag Sea, I shall merely say 

 that if the Pholades (in their Crypts) , Mytilus, and Purpura, indicate a 

 littoral zone, so also do the Brachiopoda (vide Mr. Jeffreys), the 

 Fusi, F. Turtoni, F. Largillierti, F. Norvegicus, Cassidaria bicatenata, 

 Buccinopsis, and other genera indicate deep water. A submergence 

 of the former would allow the fauna of the latter to accumulate. I 

 see no other way out of the dilemma.' 



Contrary to the views of Mr. Prestwich, I find the ''characteristic 

 land and freshwater features of the Norwich Crag " set in South of 

 the Iken ridge. Of 23 species of this class, Mr. Prestwich himself 

 quotes 10 from Butley and Waldringfield. As the exertions of the 

 Norwich and Suffolk geologists (whose names are legion) have 

 brought up the Mollusca of this Trans-Iken Sea to 170 species, and 

 the Cis-Iken area of the same age (our Upper Crag, op. cit. p. 261) 

 only musters 220, I do not think it can be considered as much 

 '• poorer." ^ 



^ A similar condition obtains in the Post-Pliocene clays of Belfast. Mr. Stewart 

 informs me that the base is characterized by Fholas crispata overlaid by a zone of 

 Thracia convexa. 



^ Is not " Bulimus " noted as occurring at Bulchamp an error ? 



