10 GENERAL ACCOUNT OF THE DEPOSITS. 



others are the marks of where 'episites' such as serpulse and 

 polyzoa have been attached to the inner surface of the original 

 shell; others again are probably the work of boring creatures, 

 especially sponges, but the great variety and the many peculiarities 

 of type 1 that occur, and their constant association with phosphatic 

 nodules are facts not sufficiently explained by the accumulated 

 work of all the above-mentioned agents 2 . I have however no 

 further explanation to offer. 



An analysis of the coprolites by Voelkler may be consulted 

 in Prof. Bonney's Cambridgeshire Geology, p. 25, where it will be 

 seen that these "red coprolites" contain about 40 or 50 per cent, 

 of phosphate of lime 3 . 



Distribution of the Neocomian Coprolites. 



The phosphatic nodules are far from being limited to the areas 

 around Cambridge and Bedford, where they have, however, alone 

 been worked. Precisely similar ones are found in the Lower 

 Greensand at Hunstanton, Ampthill, and Farringdon, in the 

 pebble beds at Godalming and Redcliff (Isle of Wight), and in the 

 Tealby section in Lincolnshire. In the last-mentioned locality 

 they form zones of 'coprolites' along the junction lines of the 

 Neocomian series both with the Kimmeridge clay below and the 

 red chalk above 4 . 



The nodules of the Downham Market coprolite-bed are of 

 quite a different character from these as described in a later page, 

 and we shall find reason for believing this bed to be of a different 

 age from the Upware rock. But crossing the N. Sea to the Bruns- 

 wick area and the Harz of Northern Germany we again find at 



1 I have seen them in the Cambridge Greensand with all the beautiful symmetry 

 of a fern frond. 



2 These structures are found in the Lower Greensand 'coprolites' of Upware, 

 Brickhill, Potton, Farringdon and Schoeppenstedt (N. Germany), and in the more 

 recent phosphatic nodules of Downham Market, the Cambridge Greensand, Bucking- 

 hamshire Gault, and the Mammillaris zone of the Ardennes chain. 



3 The 'Black Coprolites' of the Cambridge Greensand (above the gault) are 

 much richer, containing about 50 — 60 per cent, of phosphate of lime. 



4 Since the time when I first found these nodules, five years ago, Mr A. J. Jukes 

 Browne, of H. M. Geological Survey, has independently discovered the lower seam 

 above mentioned, in several places, so as to demonstrate its value in stratigraphy. 



