Vol. 62.] PHOSPHATIC CHALKS OP WINTEEBOUENE AND BOXFORD. 499 



23. The Phosphatic Chalks of Winterbourne and Boxfo 

 (Berkshire). By Harold J. Osborne White, E.Gr.S., an 

 Llewellyn Treacher, F.G.S. (Read April 25th, 1906.) 



Contents. 



Page 



1. Introduction 499 



II. Exposures in the Parish of Winterbourne 501 



III. Exposures in the Parish of Boxford 511 



IV. Concluding Eemarks 520 



I. Introduction. 



In the latter part of July 1905 we remarked, among the fossils 

 exhibited in the recently-founded Museum at the Cloth Hall, New- 

 bury, a group of guards of the belemnoid Actinocamax granulosus 

 (Blainville), labelled 'Winterbourne'* — the name of a village 3| miles 

 to the north-west of the above-named town. To us, these speci- 

 mens were objects of more than usual interest, inasmuch as our 

 examination of the Upper Chalk in the western part of the London 

 Tertiary Basin, so far as it then extended, had shown us (1) that 

 Actinocamax granulatus was a rare fossil in that area ; (2) that it 

 was there confined to beds of the Marsupites-~B&n& and of later age ; 

 and (3) that such beds, although well-developed to the south of 

 the Kennet, were cut out, by the Eocene overstep, to the north of 

 that river, along a line passing 2 or 3 miles south of the parish 

 of Winterbourne. Assuming the guards to be correctly labelled, 

 they seemed to indicate the existence of an outlying mass of 

 Marsiqntes-, or newer, Chalk rather rich in belemnoids, within a tract 

 of country where the Eocene deposits were known to be generally 

 in contact with some part of the older, Micraster cor-anguinum- 

 Chalk ; and as we had but recently given some attention to just 

 such a mass in the shape of the Phosphatic Chalk of Taplow, the 

 possibility of the recurrence of phosphatic conditions near Newbury 

 at once presented itself to our minds. 



On our making enquiry of the Honorary Curator, Mr. Frank 

 Comyns, M.A., he informed us that the specimens of Actinocamax 

 had been presented by Miss M. Baylis, of Wyfield Manor, Boxford, 

 a lady with whom he was so good as to place us in communication. 

 We visited Boxford in August, when Miss Baylis kindly showed us 

 a small but interesting collection of local Chalk-fossils, and described 

 the position of the excavations whence they were derived. The 

 examples of Actinocamax (of which the collection contained about 

 a dozen) had all been obtained, we were informed, from a single 

 working ; and this proved to be a small, disused field-pit, a quarter 

 of a mile north-west of Winterbourne Church, and visible from 

 none of the neighbouring roads. Though the face of the pit was 

 stained by rain- wash, it could be seen at a glance that flints, which 

 abound in most of the other excavations in the district, were here 



