PART II. CHAPTER XIV. 



177 



Older Pliocene Strata English Crag. 



as in the colder regions. A large volute, called Voluta Lam- 

 berti, (Fig. 135.) may seem an exception ; but it differs in form 

 from the volutes of the torrid zone, and may, like 

 Fig-. 135. the large Voluta Magellanica, have been extra- 

 tropical. 



When I first submitted the shells of the crag to 

 M. Deshayes, in 1829, he recognized their general 

 resemblance to the fauna of the German ocean, and 

 determined that out of 111 species there were 45 

 identical with those now living. Dr. Beck, on the 

 other hand, who has since seen much larger collec- 

 tions, considers that almost all the species are dis- 

 tinguishable from those now living, and this subject 

 is still under discussion. 

 Valuta LamUrti, Jt has been asked whether, as the upper and 

 young individ. j^^^^ ^^^^ Suffolk differs greatly in mineral 

 composition and fossils, they may not belong to two different ter- 

 tiary periods. To this I may reply, that the general character 

 of the shells is the same, and by no means leads to such a con- 

 clusion. The two deposits may have been going on contempo- 

 raneously under different geographical conditions in the same 

 sea. One region of deep and clear water, far from the shore, 

 may have been fitted for the growth of certain corals, echini, 

 and testacea ; while another shallower part nearer the shore, and 

 more frequently turbid, or where sand and shingle were occa- 

 sionally drifled along, may have been favourable to other species. 

 After this, the region of deep and tranquil water becoming shal- 

 low, or exposed to the action of waves and currents, a formation 

 like the coralline crag may have been covered over with sandy 

 deposits, such as the red crag, and many fossils of the older beds 

 may have been washed into the newer strata. If a considerable 

 lapse of time intervened in a particular spot between the conver- 

 sion of a deep sea into a shoal, some small change in organic 

 life may have taken place, and consequently the distinctness in 

 character of the fossils of the two formations may be derived 

 from two causes, first and principally the difference of geo- 

 graphical conditions, and, secondly, that law of the coming in 

 and going out of species which was alluded to in the last chap- 

 ter, (p. 161.) 



The area over which both divisions of the crag can be traced 

 is too small to enable us to arrive at satisfactory conclusions on 

 a question of such magnitude ; but the section given above (p. 

 175.) shows distinctly that, near Sutton, the lower crag had suf- 

 fered much denudation before the deposition of the red crag. At 

 D (Fig. 128.) there is not only a distinct cliff, eight or ten feet 



