Ch. XIV.] SUFFOLK CKAG. 169 



to a very peculiar type, which seems to characterize the state of the living- 

 creation in the north of Europe during the Older Pliocene era. 



For a large collection of the fish, echinoderms, shells, bryozoa, and cor- 

 als of the deposits in Suffolk, we are indebted to the labors of Mr. Searles 

 Wood. Of testacea alone he has obtained 230 species from the Eed, and 

 345 from the Coralline Crag, about 150 being common to each. The 

 proportion of recent species in the new group is considered by Mr. Wood 

 to be about '70* per cent., and that in the older or Coralhne about 60. 

 When I examined these shells of Suffolk in 1835, with the assistance of 

 Dr. Beck, Mr. George Sowerby, Mr. Searles Wood, and other eminent 

 conchologists, I came to the opinion that the extinct species predominated 

 very decidedly in number over the living. Recent investigations, how- 

 ever, have thrown much new light on the conchology of the Arctic, 

 Scandinavian, Biitish, and Mediterranean Seas. Many of the species for- 

 merly known only as fossils of the Crag, and supposed to have died out, 

 have been dredged up in a living state from depths not previously ex- 

 plored. Other recent species, before regarded as distinct from the nearest 

 allied Crag fossils, have been observed, when numerous individuals were 

 procured, to be liable to much greater variation, both in size and form, 

 than had been suspected, and thus have been identified. Consequently, 

 the Crag fauna has been found to approach much more nearly to the re- 

 cent fauna of the Northern, British, and Mediterranean Seas than had 

 been imagined. The analogy of the whole group of testacea to the Eu- 

 ropean type is very marked, whether we refer to the large development 

 of certain genera in number of species or to their size, or to the sup- 

 pression or feeble representation of others. The indication also afforded 

 by the entire fauna of a climate not much warmer than that now pre- 

 vailing in corresponding latitudes, prepares us to believe that they are not 

 of higher antiquity than the Older Pliocene era. 



The position of the Red Crag in Essex to the subjacent London clay 

 and chalk has been already pointed out (fig. 148). Whenever the two 

 divisions are met with in the same district, the Red Crag lies uppermost ; 

 and, in some cases, as in the section represented in fig. 149, which I had 

 an opportunity of seeing exposed to view in 1839, it is clear that the 

 older or Coralline mass b had suffered denudation, before the newer for- 

 mation a was thrown down upon it. At D there is not only a distinct 



rig. 149. 



Eamsholt. 



Section near Ipswich, in Suffolk. 

 a. Red Crag. b. Coralline Crag. c. London Clay. 



chff, 8 or 10 feet high, of Coralline Crag, running in a direction N. E. and 

 S. W., against which the red crag abuts with its horizontal layers ; but 



* See Monograph on the Crag Mollusca. Searles Wood, Paleont. Soc. 1848. 



