Vol. 6 2. J PHOSPHATIC CHALKS OF WINTEKBOTJRNE AND BOXFOHD. 503 



an inch in diameter) are scattered through the rock, which, in its 

 less compact portions, is even more harsh and gritty to the touch 

 than the chalk below. In the midst of the rock the green nodules 

 are firmly welded to their matrix ; near the top they may often be 

 detached with little difficulty. The appearance of this chalk recalls 

 that of the Chalk Rock. Where hardest, the rock is rather closely 

 and rectangularly jointed, and its gnarled, undulate, well-defined 

 top bears the impressions of sponges of the Ventriculites-type ; it is 

 well- en crusted with adherent valves of Ostrea, Spondylus, and 

 Plicaiula ; and is covered with a faintly-glossy brown wash of 

 phosphate, which penetrates to a depth of a quarter of an inch or 

 more. Dendrites of manganese-oxide occur on the joint-surfaces. 



The chalk of bed (5) — seen for about 4 feet in the highest part 

 of the section — is firm and white, or pale greyish- white, with black 

 specks. It is closely jointed into small cuboidal or flaggy blocks, 

 and much stained by earthy wash from above. Very harsh and 

 gritty in its lower parts, it gradually becomes soft and fine-grained 

 upwards, and samples from the top are hardly to be distinguished 

 from ordinary chalk by the naked eye. Greenish-yellow nodules 

 with brown coats and the little angular concretions are common 

 in the lowest 18 inches, but become scarce above; and brown 

 granules, though common enough in the lowest 6 inches, are else- 

 where much less apparent than in the beds lower down in the 

 section. 



The Chalk is covered by a sandy loam, with flint-nodules and 

 broken flints, which descends into shallow pockets. At the bottom 

 of this Drift there are a few unworn flint-nodules, of elongate form, 

 which have doubtless been derived from the Chalk formerly inter- 

 vening between the highest beds of the section and the base of the 

 Reading Series. 



Microscopic features. — When broken down with a brush in 

 water and washed clear of the fine calcareous mud, the softer 

 chalks of this section yield a bulky residue, consisting of the 

 following materials : — 



(1) Prisms of Inoceramus-shell. The great majority are un- 



phosphatized ; larger fragments of the shell occasionally are 

 partly silicified. This material is most abundant in the 

 residues from bed (3) ; least so in those from the upper part 

 of bed (5). 



(2) Foraminifera : frequently phosphatized and of a pale to 



rich dark-brown colour, often with a high polish. The 

 phosphatized examples are referable chiefly to the Textu- 

 lariidse and Globigerinidse, and usually measure between 0*1 

 and 02 millimetre in diameter. The calcareous examples 

 are mostly of the Rotaliidae, and are more numerous and 

 generally of greater size (0*3 to 0*6 mm.) than the phos- 

 phatized. Subspherical objects, which appear to be de- 

 tached cells of foraminifers, are common. 



