﻿172 Geological Society :— 



deposition of the Heading Beds. When the area of observation is 

 extended, it is found that the Uintacrhius-Chalk of that tract itself 

 lies in a structural depression. In view of the development of 

 phosphatic and of hard, rocky beds, indicative of slow and inter- 

 rupted sedimentation, in the underlying cor-anguinum-zone, it 

 seems not unlikely that this basin is an original or inherent feature 

 of the Chalk directly attributable to a local attenuation of that zone ; 

 but the authors believe the depression to be due mainly to differential 

 earth-movements, of which there are many indications. The ex- 

 posures are found in the eastern (Winterbourne) and western (Box- 

 ford) sides of a spur lying in the angle between the converging 

 valleys of the Lambourn and the Winterbourne. On the eastern 

 side the following succession is recognized : — 



1. Eeading Beds of the Borough-Hill outlier. 



2. Chalk with some flints. 1 Zone of Actinocamax 



3. Phosphatic Chalk. J quadratus. 



4. Phosphatic Chalk. Marsn P ites ' ha ' nd -\ Zone of Mar supites 



5. Very feebly-phosphatic Chalk. Uintacrinus-bajid. \ F 



6. Chalk with tabular flints. 1 Zone of Micraster 



7. Chalk with flints. J cor-anguinum. 



and on the western side : — 



1. Eeading Beds. 



2. Phosphatic Chalk. Zone of A. quadratus. 



3. Phosphatic Chalk. Marsupites-band . 1 



4. Feebly-phosphatic to normal Uintacrintts-b&rui. I Zone of Marsupites. 



Chalk. J 



5. Normal flinty Chalk. \ 



6. Phosphatic Chalk. | „ f Micraster 



7. Normal flinty Chalk. ^ one 0t MlC7astei 



8. Phosphatic Chalk. [ ^r-angmnum. 



9. Normal flinty Chalk. ; 



The maximum thickness of the Phosphatic Chalk Series is about 

 130 feet. Detailed accounts of the various exposures are given, as 

 also lists of fossils from the various bands, and an account of the 

 microscopic features of washed residue from the softer chalks of the 

 pit a quarter of a mile north-west of Winterbourne Church. This 

 yields: (1) pieces of Inoceramus-sheW., the majority unphosphatized ; 

 (2) foraminifera, frequently phosphatized; (3) angular chips of scales, 

 bones, and teeth of fishes ; (4) irregular, angular or subangular lumps 

 and platy pieces of calcite, probably in the main fragments of oysters ; 

 (5) rod-like objects, smooth, cylindrical, or tapered — probably 

 spines of echinoids ; (6) coprolites of small fishes, etc. ; (7) tests of 

 entomostraca ; (8) quartz in subangular and well-rounded grains ; 

 ^9) black granules, apparently of iron-oxides; (10) rich-brown, 

 polished phosphatic concretions ; and (11) dull-green grains, im- 

 perfectly rounded. These constituents are enumerated as nearly as 

 possible in order of abundance. 



The Winterbourne-Boxford phosphates have a known range in 

 time considerably greater than those of Taplow. Their advent far 

 down in the cor-anguinum-zone is especially interesting: lor in 



