Saunders — Geology of South Bedfordshire. 155 



hard grey limestone, ranging from a foot to eighteen inches in thick- 

 ness. The northern approach shows an anticlinal in these lime- 

 stone bands. The upper beds of brown clay contain very many 

 small crystals of selenite, which sometimes constitute one-third of 

 the entire mass. In the lower beds the crystals are rare, but much 

 more regular in form and beautiful in appearance, and also much larger, 

 one specimen measuring about six inches in its major diameter. The 

 fossils observed were bones of Plesiosaunis, one vertebra of which 

 weighed ten pounds, spines of several species of Echini, Ostrea 

 carinata and various other species, Pentacrinites, Belemnites, Gryphea, 

 and Ammonites Calloviensis. 



Near the village of Flitwick are two cuttings in the Lower Grreen- 

 sand, consistiag of white and yellow sands, alternating with bands 

 of ironstone. These beds extend beyond Sandy, in a north-easterly 

 direction, and to Leighton south-westwards. At Silsoe, five miles 

 east from Flitwick, are beds of a brown compact sandstone, which 

 furnish good building material ; these are also of Lower Grreensand age. 



A short distance south from Westoning, the coprolitic bed of the 

 Lower Grreensand is exposed,^ over which is a bed of dark heavy clay 

 (Gault?),2 which in its turn is capped by a bed of drift sand and 

 gravel. This coprolitic bed is worked in several places in the 

 immediate vicinity for its phosphatic nodules, and furnishes the 

 usual fossils characteristic of this stratum. At Harlington is a cutting 

 in the drift, but not sufficiently deep to disclose the subjacent forma- 

 tion. Between Harlington and Chalton is a cutting in the Totternhoe 

 stone, a local representative of the chalk marl.^ This occurs in a hill, 

 isolated from the general range of hills that form the north-west 

 escarpment of the Chalk formation. At Chalton is an extensive 

 excavation, upwards of a mile in length, through the range of hills 

 that constitute the watershed of the district. The combes, that have 

 been eroded by the action of the springs that rise at the base of 

 these hills, have many of them great local celebrity on account of 

 their picturesque scenery, and the lovely landscapes that may be 

 seen from the summits of the surrounding hills. The Totternhoe 

 stone is exposed at the north-west end of the cutting at Chalton, 

 where it is hard, compact, rather sandy, and of a light brown colour. 

 The deepest part of the excavation, where it is about seventy feet 

 deep, exposes the Lower Chalk, which is lighter in colour and less 

 compact than the chalk marl, beneath which is a bed of dark clay, 

 containing many pyrites. It is somewhat doubtful whether this bed 

 should be classed with the Gault or Chalk-marl, it has a very strong 



1 See Rev. P. B. Brodie's paper " On the Phosphatic Nodules in the Lower Green- 

 sand at Sandy, Bedfordshire."— Geol. Mag. Vol. III.> 1866, p. 153. 



• See also Mr. J. F. Walker's paper " On a Phosphatic Deposit in the Lower Green- 

 sand of Bedfordshire," in the Ann. and Mag. Nat. Hist. 3rd series, vol. 18, 

 Novemher, 1866. — Edit. 



2 Or Boulder-clay ?— Edit. 



> Totternhoe stone is not a local representative of the chalk-marl. It is the top bed 

 of chalk-marl through Bucks, and Berkshire ; there is eighty feet of chalk-marl below 

 it. See Mr. "Whitaker's paper thereon, Quart. Journ. Geol. Soc, vol. ixi. p. 398 

 (1866).— Edit. 



