478 Reports and Proceedings — 



The upper division has its peculiar forms, such as Modiola modiolus, 

 Astarte compressa, A. sulcata, A. elliptica. Other shells are more 

 abundant which in the lower are scarce ; here they occur as if in 

 their " life-zone," instead of as single valves, worn and broken — 

 such as Tellina ohliqua, Astarte horealis, Venus fasciata, Cardium 

 Gcernlandicum, Cyprina Islandica, Bhynchonella psittacea. 



It is only in respect of one shell (Tellina ohliqua) that the forms of 

 the upper division have not been recognized as living ; and with 

 respect to distribution, the northern facies of the upper assemblage 

 is more strongly marked than that of the lower ; lastly, they indicate 

 a somewhat greater depth of water. 



Mr. S. Wood, jun., admits this division; "the upper bed at Nor- 

 wich," he says, "is the Chillesford shell-bed." 



Chillesford Crag. — In 1849, Mr. Prestwich made known some 

 marine beds in the parishes of Iken and Chillesford, either yellow 

 sands or laminated micaceous clays. At Iken these beds are super- 

 posed upon a worn surface of the older or Bryozoan Crag. There 

 is no such direct evidence as to their relation to the Eed Crag ; but 

 there is no doubt that they are uncomformable to both divisions. 



These beds are in striking contrast to the true Crag, in respect of 

 their composition 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. S. Wood 

 recognized the Arctic character of the assemblage, and considered 

 the beds posterior to the Eed 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. 



Mr. 0. Fisher, from a careful study of the country from Orford to 

 Thorpe, convinced himself that the " Chillesford Crag" was in an 

 intermediate position between true "Eed Crag" and the "Fluvio- 

 marine Crag" at Thorpe, near Aldborough. Assuming this to be of 

 the same age as that of Norwich, his arrangement is as follows, 

 opposed to which are the results of Mr. S. Wood's examination of 

 the same district in the following year : — 



0. Fisher, 1865. S. Wood, 1866. 



Fluvio-marine, or Norwich Crag. 



M;SS:«Sg«n } ChiUesfordClay. 



Red Sands. Fluvio-marine Crag. 



Red Crag. 



Differences of opinion as to detail, both of facts and inferences, 

 might be cited, as is well-known to those geologists who have at- 

 tended to this very complicated portion of the geological record ; 

 but thus much seems to have been ascertained, that the so-called 

 ( .liillesford Crag is rather a subordinate member of the marine Glacial 

 I)eriod 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. 



