464 



PLIOCENE. 



m< 



been restricted. As, however, the beds above noted are all intimately connected, 

 the term Norwich Crag Series may conveniently be applied. The bands of clay 

 (3) have no doubt served in some instances to protect the shells from 

 destruction by percolating waters, for when these occur in the pebbly gravel (4) they 

 are generally in the form of casts. 



Mammaliferous Stone-bed. — At the base of the Fkivio-marine 

 Crag there is usually found a bed of 

 unworn and partially rolled flints, termed 

 by Mr. John Gunn the 'Stone bed.' It 

 rests on the Chalk, the surface of which 

 is occasionally bored by Pholas and Anne- 

 lides. This bed yields numerous Mam- 

 malian remains, including Mastodon Arveni- 

 ensis, ^ Elcphas vitridionalis, E. antiquiis, 

 Hippopotamus major, Gazdia aiiglica (Ante- 

 lope),''' Cervus Siittommsis, C. P\i/coHi?i, Tro- 

 gonthcrium Cuvieri, Arvicola vitermedhis, Eqims 

 cahallits fossilis, Felis pardoides, HycEna antiqua, 

 etc. On first thoughts it might strike one 

 that this bed was of the same character as 

 the Suff"oIk Bone-bed previously described 

 (see p. 459). This is not the case ; the 

 bones are not phosphatized, and, although 

 Mr. Whitaker has found one or two copro- 

 lites in the base of the Crag at Thorpe near 

 Norwich, these phosphatic nodules are rare. 

 Moreover, the state of preservation of the 

 bones is in favour of their belonging to the 

 period, and not being derived from any 

 -j I earlier deposit. The bones are frequently 



I ^ found on, as well as in, the Stone-bed, and 

 ' > occasionally in the overlying strata. Crag 

 I I o shells, especially Pecten opercidahs, Tdlina 

 J"i ^ crassa, JMytilus editlis, Tivphon antiquus, etc., 

 are interspersed with the flints, and occur 

 even in crevices of the Chalk. Hence we 

 are justified in regarding the Stone-bed as 

 the marine basement-bed of the Crag.^ The 

 bones, like the land and freshwater shells in 

 the Crag, may have been carried into the 

 4(--( It do sea by rivers. 



Fluvio-marine Crag. — The Fluvio-marine 

 Crag, so termed by Lyell, consists of bufl" 

 shelly sands and shingle, often false-bedded, 

 having a thickness of 5 or 10 feet, and con- 

 taining an admixture of marine and fresh- 

 water MoUusca. The influence of freshets 



>^ 



M 



1 See Dr. H. Falconer, Q. J. xiii. 307. 



- E. T. Newton, Q. J. xl. 280 ; Geol. Norwich, p. 55. 



3 See O. Fisher, G. Mag. 1868, p. 546; F. W. Harmer, Q. J. xxxiii. 139. 



