THE CAMBRIDGE GAULT AND GREENSAND. 263 



The following fossils in light phosphate were picked up on the 

 heap, amongst which the most abundant was Avicula gryphceoides ; 

 this could be taken from the bed itself, with the delicate shell com- 

 pletely preserved. 



Ammonites auritus, Sow. 



Studeri, Pict. 



Mantelli, Sow. 



Hamites intermedins, Sow. 

 Nautilus, sp. 



Belemnites minimus, Sow. 

 Pterodactylus, sp. 



Avicula gryphseoides, Sow. 

 Plicatula pectin oides, Sow. 



sigillina, Woodw. 



Ostrea vesicularis, Sow. 

 Terebratula biplicata, Sow. 

 Kingena lima, aVOrb. 

 Parkeria (flat sp.). 



This is the most westerly coprolite-pit in Bedfordshire ; nor is any 

 thing seen of the Cambridge nodule-bed beyond this, though I have 

 reason to believe that it still continues in a similar form as far as 

 Harlington on the edge of Sheet 46, N.E. 



At the next exposure, however, which is in a brick-pit at Fancott, 

 nearly two miles S.W. of Harlington, a very different section is to 

 be seen ; this, in descending order, was : — 



4. White marl or clunch, becoming grey below, and passing 



into no. 3 about 6 feet. 



3. Greyish clay with iron staining in the j oints 3 „ 



2. Bluish sandy clay with a few light-buff-coloured coprolites 



scattered through it 6 ,, 



1. Dark blue clay with scattered coprolites 2 ,, 



I got a man to dig in this bottom bed ; and we turned up some 

 coprolites and Avicula gryphceoides ; he assured me also that about 

 10 feet down black coprolites became so numerous as to form a 

 regular seam or bed. This may be the bed which cropped out in* the 

 pit at Barton ; and at any rate I think it has furnished many of the 

 coprolites found there. 



The passage here is complete from top to bottom of the section, 

 no break or discontinuity being visible anywhere ; but for conveni- 

 ence' sake I would group the blue beds with the Gault, and the grey 

 beds, nos. 3 and 4, with the Chalk-marl or Totternhoe Marl, as 

 Mr. Whitaker terms it here*. They certainly cannot be called 

 Upper Greensand. 



I did not see the junction of the Chalk and Gault again for some 

 miles, until, reaching the foot of the N.W. slope of Totternhoe Hi]l, 

 I found that a well had lately been dug to a depth of 14 or 15 feet. 

 The material thrown out was a bluish sandy clay like that in the 

 brick-pit at Fancott ; the sandiness was caused by fine gritty and 

 micaceous spangles ; no green grains were visible either here or at 

 Fancott. 



We are now within the area which has been mapped by the 

 Geological Survey ; and on referring to their Sheet 46, S.W., I was 

 glad to find the Chalk-marl coloured as immediately succeeding the 

 Gault to the exclusion of the Upper Greensand. I also learnt from 

 Mr. Whitaker that he had always looked upon the Cambridge nodule- 

 bed as forming the base of the Chalk-marl, and that he had so indi- 



* " Chalk of Buckinghamshire," Quart. Journ. Geol. Soc. vol. xxi. p. 339. 



