346 



G. E. Grimes — Radiolarians in Chalk. 



top of the Fuller's Earth, and is mapped by the Geological Survey 

 as equivalent to the Sandgate Beds of East Kent ; but this is 

 disputed by some geologists. As the rock forms the surface of 

 the dip slope of the Lower Greensand at this place it has been 

 considerably denuded, so that its thickness varies from to about 

 27 feet. When examined in thin sections with the microscope the 

 rock is found to be composed chieflj' of broken sponge spicules, and 

 with these Foraminifera (mostly infilled with glauconite and in 

 many cases having the original test), glauconite grains and casts, 

 fragments of tests of Echinodermata, some grains of quartz, and 

 more or less iron oxide. In a few slides globate spicules of 

 bleodites were also noticed. The silica in the sponge spicules 

 mostly assumes in a greater or less degree the globular form, which 

 was first noticed by Dr. G. J. Hinde in his paper " On Beds of 

 Sponge Remains in the Lower and Upper Greensand." ^ 



X'^OO 



y-ZOO 



ZOO 



xZOQ 



Eadiolaiians from the Greensand of Redhill and Reigate. 



Fig. 1. — Ca^posphcera JVeocomiensis, sp.n. From the Fuller's Earth Rock Bed, 



Lower Greensand, Redhill, Surrey, x 400. 

 Fig. 2. — Ealiomma sp. ? From the Fuller's Earth Rock Bed, Lower Greensand, 



Redhill. x 200. 

 Fig. 3. — Carposphmra, sp. From the Upper Hearthstone, Upper Greensand, 



Reigate Hill, Surrey, x 200. 

 Fig. 4. — Carposphcera, sp. From the Lower Hearthstone, Upper Greensand, 



Reigate Hill, x 200. 



Eadiolaria were most numerous in the rock from the pit at the 

 top of Redstone Hill and on the south side of the road between 

 Redhill and Nutfield, where there were as many as seven or eight 

 in a section of a little over a square inch in area. The Radiolarians 

 in this bed mostly belong to the genus Carposphcera, Haeckel, with 



> Phil. Trans. Royal Soc, part ii, 1885, p. 427. 



