CORALLINE CRAG. 457 



long attracted the attention of collectors, on account of the 

 abundance of fossils at certain localities, and the readiness with 

 which they may be obtained. 'Crag' is a Suffolk term for gravel, 

 the shelly portions of which have been in former years largely dug 

 as ' marl ' for agricultural purposes.^ 



In 1835 Mr. Edward Charlesworth gave the first good account 

 of the Crags in Suffolk, and he then proposed the terms ' Red 

 Crag' and 'Coralline Crag' to distinguish them from one another, 

 and from the Norfolk or Norwich Crag, to which in 1836 he applied 

 the term ' Mammaliferous Crag.' ^ Since this date the labours of 

 Mr. S. V. Wood, jun., Mr. F. W. Harmer, Prof. Prestwich, Mr. 

 Clement Reid, and others, have added greatly to our knowledge 

 of the structure of the deposits ; while for the minute description 

 of their Molluscan remains we are indebted to Mr. Searles 

 Wood, sen.^ 



CORALLINE CRAG. 



r 



The Coralline Crag consists of yellow calcareous shelly sands, 

 having a thickness estimated at from 40 to 80 feet. The beds are 

 often ' piped ' like the Chalk. 



The following general divisions are abbreviated from those given 

 by Prof. Prestwich : * — 



Upper or I J. Sand and comminuted shells, with remains of Polyzoa, 



Polyzoan (Bryozoan) ! sometimes forming a soft building-stone, showing 



Zone. p,6 leet. ( much false-bedding. 



r6. Sand with small shells and seams of comminuted shells. 



5. Sands with numerous Polyzoa, often in the original 



position of growth, and containing also small shells 



Lower or and Echini. 



Shell zone. - 4. Comminuted shells, large entire or double shells, and 



47 feet. thin bands of limestone. 



Marly beds with well-preserved shells. 



Comminuted shell-beds with Cetacean remains and 



Polyzoa. 



f^ rr 11 T> , 1 f I. Bed with Phosphatic nodules (' Coprolites,') and Mam- 

 Suffolk Bone-bed. { ,• • v r ' / 

 ( malian remams. 



It has been questioned whether so thick a series of strata is developed at any one 

 locality ; ° but Mr. P. F. Kendall is of opinion that the thicknesses of both Coralline 

 and Red Crags have been underestimated. 



1 The term Crag Marl was used by Sowerby in 1812, Min. Conch, vol. i. 

 Supp. Index. 



2 Phil. Mag. (3), vii. 81, 465 ; Rep. Brit. Assoc, for 1836 ; Proc. G. S. ii. 195. 



3 S. V. Wood, Crag Mollusca (Palreontogr. Soc), 1848-61, Supplements 1872, 

 1874, and 1879; see also Crag Polyzoa, by G. Busk, 1859, etc; A. and R. 

 Bell, P. Geol. Assoc, ii. 185, 270. 



* Q. J. xxvii. 121. 



* Lyell, Student's Elements, 1871, p. 173. 



