FORMATION. 11 



THE CKAG FOBiLiTION. 



1. Mammaliferous or Nortcich Crag. 2, Red Crag. 

 3. Coralline Crag. 



The deposits to which the term Crag has been applied iu 

 Norfolk and Suffolk, were formerly considered as belonging 

 to one period. ^Ir. Charlesworth, however, after a careful 

 examination of the localities and organic remains, su^ested 

 the triple division as given above. Mr. Lvell places the 

 Upper or MammaUferous Crag in the Older Pleiocene, 

 and the Eed and Coralline Crag in the ^Miocene strata. 

 The Mammaliferous Crag consists of sheUv beds of sand, 

 laminated clay, and loam, with layers of flinty shingle, 

 reposing on the chalk, and generally covered with a thick 

 bed of gravel. This stratum contains above one hundred 

 species of testacea, about twenty of which are land and 

 fresh-water shells, and associated with these are numerous 

 remains of Fish {Platax, Myliobates), and Mammalia 

 (Mastodon, Elephant, Horse, Pig, &c.), and also bones of 

 Birds. The Eed Crag is a deep ferruginous sheUv sand, 

 and loam, with an abundance of marine shells, many of 

 which are rolled and frequently comminuted, and the 

 layers are sometimes obliquely arranged, proving an irre- 

 gular movement during their deposition. Between two 

 and three hundred species of testacea are known from 

 this bed {Fusm contrarius, Mnrex akeolatm, are abun- 

 dant), and bones and teeth of fishes {Carcharim, Mylio- 

 bates, &c.). The Coralline Crag is a mass of shells 

 and corals in calcareous sand, or compact and formino- 

 flaggy beds of limestone with bands of greenish marl; 

 some of the harder portions are used as a building stone. 

 Corals, Zoophvtes, Echinoderms, and about foiu* hundred 

 species of shells constitute the fauna of this bed, which 



