THE CAMBRIDGE GAT7LT AND GREENLAND. 257 



great opportunities of prosecuting. I wish therefore in the first 

 place to say a few words regarding the circumstances under which 

 this paper came to be written. 



It was in 1872 that the idea first occurred to me that the so-called 

 Cambridge "coprolites" had not originated where they are now 

 found, but had been derived from some part of the underlying 

 Gault. This supposition was confirmed by subsequent conversation 

 on the subject with the Eev. T. G. Bonney, who had, I found, for 

 some years held the same opinion regarding their origin. His views 

 were published in a paper read before the Geologists' Association in 

 February, 1872, in which he gives a general review of the contents 

 of the bed, notices the large proportion of Gault forms, and draws 

 attention to the waterworn character of these fossils and to the 

 eroded surface of the Gault below. This excellent paper, by its 

 general survey of the questions connected with the Cambridge bed, 

 was admirably fitted to clear the way for further investigations. It 

 only remained therefore to extend the area of observation beyond the 

 immediate neighbourhood of Cambridge, and to institute a thorough 

 palseontological comparison between the Cambridge fauna and those 

 of other beds between the same horizons. 



With the view of assisting Mr. Bonney I at once commenced this 

 latter undertaking in the Woodwardian Museum ; the work, however, 

 did not progress rapidly, till the presence of Mr. F. G. H. Price in 

 Cambridge enabled me to obtain from him more accurate information 

 regarding the Gault fauna, which he has so systematically worked 

 out at Folkestone*. This locality I had also the advantage of visiting 

 with Mr. Price, and of collecting from the Upper Gault nodules and 

 fossils identical with those on our Cambridge " coprolite " heaps. 

 My next step was to try and find the representative of this Upper 

 Gault, with its sandy bed, in the more northern area ; and, acting on 

 information kindly given me by Mr. Whitaker, I proceeded to Ched- 

 dington, in Bucks, and thence through Bedfordshire to Hitchin. 



In this traverse I was fortunate in finding the beds of which I 

 was in search, and also succeeded in fixing the extreme south-west 

 limit of the Cambridge nodule-bed. 



Having thus acquired sufficient material for publication, I com- 

 municated the results to Mr. Bonney, who had already given the 

 subject so much consideration, and with whom it would have afforded 

 me much pleasure to be associated. He, however, generously waived 

 his participation in the proposed paper, and persuaded me to publish 

 the results of my own investigations. 



In doing this I propose first to examine the physical relations of 

 the Gault, Greensand, and Chalk in the counties of Cambridge, 

 Bedford, and Bucks, and to compare them with the same formations 

 in the south of England ; secondly, to examine the paheontological 

 relations between the Cambridge fauna and that of other beds be- 

 tween the Lower Gault and Chalk-marl (Allien and Rhotomagieri), 

 both in England and on the Continent. 



* See Quart. Journ. Geol. Soc. vol. xxx. p. 342. 



