170 



OLDER PLIOCENE FORMATIONS. 



[Ch. XIV. 



this cliff occasionally overhangs. The rock composing it is drilled every 

 where by Pholades, the holes which they perforated having been after 

 wards filled with sand and covered over when the newer beds were thrown 

 down. As the older formation is shown by its fossils to have accumulated 

 in a deeper sea (15, and sometimes 25, fathoms deep or more), there must 

 no doubt have been an upheaval of the sea-bottom before the cliff here 

 alluded to was shaped out. We may also conclude that so great an 

 amount of denudation could scarcely take place, in such incoherent ma- 

 terials, without many of the fossils of the inferior beds becoming mixed up 

 with the overlying crag, so that considerable difficulty must be occasion- 

 ally experienced by the palaeontologists in deciding which species belong 

 severally to each group. 



The Red Crag being formed in a shallower sea, often resembles in struc- 

 ture a shifting sand-bank, its layers being inclined diagonally, and the 

 planes of stratification being sometimes directed in the same quarry to 

 the four cardinal points of the compass, as at Butley. That in this and 

 many other localities, such a structure is not deceptive or due to any sub- 

 sequent concretionary rearrangement of particles, or to mere lines of color, 

 is proved by each bed being made up of flat pieces of shell which he par- 

 allel to the planes of the smaller strata. 



Some fossils, which are very abundant in the Red Crag, have never 

 been found in the white or coralline division ; as, for example, the Fusus 

 contrarins (fig. 150), and several species of Murex and Buccinum (or 

 JVassa) (see figs. 151, 152), which two genera seem wanting in the lower 

 crag. 



Fig. 150. 



Fossils characteristic of the Red Crag. 

 Fig. 151. 



Fig. 152. 



flassa granulata. 

 Fig. 153. 



Fusus contrarius. Murex alveolatus. Cypraso. coccineUoides. 



Fig. 150 half nat size ; the others nat. size. 



Among the bones and teeth of fishes are those of large sharks ( Carcha- 

 rodon), and a gigantic skate of the extinct genus Myliobates, and many 

 other forms, some common to our seas, and many foreign to them. It is 

 questionable, however, whether all these can really be ascribed to the era 

 of the Red Crag. Not a few of them may possibly have been derived 

 from older strata, especially from those Upper Eocene formations to be 

 described in the next chapter, which are largely developed in Belgium, 



