474 PROCEEDINGS OF THE GEOLOGICAL SOCIErY. [June 3, 



ft. in. 



c. Layer of phosphatic nodules and fossils 1 



of. Yerj green sand 2 



e. Layer of phosphatic nodules 1 



/. Greenish rather clayey sand 2 



g. Light greenish and grey sand, reddish below 3 



A. Lignite, not constant 2 



i. Grreenish sand, resting unconfoi'mably on 2 



Jc. Highly inclined shales (Devonian). 



The junction between theGault and the Lower Greensand is usually 

 taken at the base of the phosphatic bed ; and it is generally under- 

 stood that there is a sharp lithological and palseontological break 

 between these two di^^sions. That they are well marked off from each 

 other on the large scale, in the south-east of England, is certainly 

 true ; but a careful examination of the junction will frequently show 

 that there is a very decided passage from one to the other. 



Fig. 2. — Section through Caffiers (about 5 miles). 



S. 2.S°W. N.250E. 



Caffiers. Haines. 



a. Chalk and L^pper Greensand. 

 d. PaliTeozoie. 



b. Gault. c. Lower Greensand. 

 X X . Sea-level. 



The phosphatic bed at Copt Point belongs evidently to the Gault ; 

 its fossils clearly place it there. But in the sands below are found 

 phosphatic nodules with Gault-hke fossils (also phosphatic), which, 

 therefore, should also be referred to the Gault. Ammonites mam- 

 millaris, Schloth., A. Beudantii, Brong., and Inoceramus SaJomoni, 

 D'Orb., are very common in these sands and in the coarse calcareous 

 grit below. IT. Gaudry * has noticed the occurrence of A. mammil- 

 laris, in the sands at Polkestone and Wissant ; he proposes to separate 

 them from the Lower Greensand and to place them with the Gault. 



The hthological passage is not less evident in some places : at Copt 

 Point, where there is only one line of phosphatic nodules, it is not 

 difficult to fix upon a boundary between the two beds ; at Wissant, 

 it is not so definite, still less so at Caffiers ; and where there are two 

 or more well-marked layers of nodules it is difficult to decide at 

 what point to take the junction. A section open about three years 

 since at the west end of the Lees, Folkestone, showed three beds of 

 nodules, the overlying clay being true Gault, and the intermediate 

 beds in descending getting more sandy ; the sand below the third bed 

 of nodules belonged to the true Folkestone beds, and contained a 

 small nest of nodules in one place. The two upper beds of nodules 

 contained bored wood. 



* Bull. Soc. Geol. de France, ser. 2. voL xvii. 1860, p. 32. 



