Walter Keeping — Neocomian Sands at Brickhill, Beds. 373 



sometimes hardened by iron oxide or calcium carbonate ; the former 

 along lines of oblique lamination, the latter usually in irregular 

 masses, which are rejected as useless. As I saw it, the lower ten 

 feet was of a dull greenish or grey colour, passing in an irregular 

 manner into the redder portions above ; but there is no definite 

 divisional line separating the two, the difference in colour being 

 probably due to the oxidation of the iron in the more superficial part. 



As at Potton, these sands repose upon the Oxford-clay, the Grypliea 

 dilatata being abundant in the clay beneath. 



Unlike any other coprolite working known to me, there is no "seam " 

 here, but the phosphatic nodules are scattered through the entire 

 thickness of the section, 1 and they are separated by sifting the whole 

 of the thirty feet of sands, except where they are too much hardened 

 by cementing substances. Thus separated, the coprolites are washed 

 in revolving perforated cylinders, and any pebbles of quartz, chert, 

 lydian stone, etc., are picked out when the material is ready for 

 grinding. The whole process is the same as that carried on at Potton 

 in Bedfordshire and Up ware near Cambridge. 



From Paheontological evidence, we have long believed the Upware 

 deposit (which has already been described in the pages of this Maga- 

 zine 2 ) to be the representative of, if not continuous with, the 

 Farringdon Sponge-bed. Now Brickhill is nearly equally distant 

 from Upware and Farringdon ; here then is the spot to settle the 

 question of their relation. 



The phosphatic nodules of Upware occur in the Neocomian Sands 

 in three seams, which are irregular and sometimes run together, 3 

 and in the Bushmoor Brickyard, 4 a few miles from Brickhill, the 

 " coprolites " may be seen similarly collected into a bed from four to 

 seven feet thick, resting on the Oxford-clay. At Farringdon copro- 

 lites are found scattered through the sands, especially towards the 

 base. 



But few fossils are to be seen among the prepared coprolites, and 

 these are mostly phosphatised casts in a much worn condition, so that 

 a glance at the heap would lead one to observe with the Bev. P. B. 

 Brodie, 5 when speaking of the Potton bed, that "every organism in this 

 phosphatic bed is evidently extraneous." Ammonites biplex is always 

 the conspicuous fossil in this condition, together with Cardium 

 striatulum, Area, and Myacites, all of which I found at Brickhill. 



But on breaking open the hard masses cemented by the carbonate 

 of lime, and also in a small patch of the section where calcareous 

 matter remained, the natives of the bed were themselves found, still 

 with their shells well preserved, and in general appearance closely 

 resembling those of Upware. The following is a list of them. 6 



1 In the lower part they are more numerous and blacker. 



2 J. F. Walker, Geol. Mag. 1867, Vol. IV. p. 309. 



3 "Walker, op, cit. p. 310. 



4 I was informed that about four years ago they bored for coal in this yard ! 



5 Geol. Mag. 1866, Vol. III. p. 153. 



6 Mr. J. F. Walker has kindly examined and confirmed my identifications of those 

 species described by him in the Geol. Mag. Vol. IV. p. 454 ; Vol. V. p. 399. 



