1865.] 



WHITAKEE BXrCKlNGHAM CHALK, 



399 



I cannot give the thickness with accuraC3\ I will now give a short 

 account of each, beginning with the lowest. 



(g). Chalk-marl. — A 

 rather brownish-white, 

 slightly sandy, clayey 

 chalk, fissile, with stony 

 layers here and there, and 

 often with fossils (notably 

 fish-scales). This is per- 

 haps 80 feet thick, and 

 mostly causes a rise of the 

 ground above the sloping 

 plain of the Upper Green- 

 sand. 



(/). Totfernlioe Stone.- 

 At the top of the Chalk- 

 marl in this district there 

 are generally two layers 

 of rathersandy limestone, 

 separated by a little marl, 

 and which are more dis- 

 tinct further north-east- 

 ward (in Bedfordshire), 

 where they are each about 

 3 feet thick. One bed is 

 always here present, but 

 I did not always see the 

 two. This stone mostly 

 yields fossils, amongst 

 which Ammonites vai'ians 

 and an Inoceramus are 

 abundant, and small, 

 hard,dark-brown nodules, 

 most likely coprolitic : it 

 is harder and darker than 

 common chalk, and con- 

 tains many small dark 

 grains ; and was once 

 largely quarried, for build- 

 ing, at Totternhoe, where 

 there are plentiful traces 

 of the workings. Most 

 of the old churches of the 

 neighbourhood were built 

 in great part of this pe- 

 rishable stone, but I be- 

 lieve that its use has been 

 long discontinued. 



Details of the occur- 

 rence of this bed will be 

 given in the ' Gcolo- 



2 E 2 



