640 Geological Society. 



The dating of this Watton Bed is discussed, after preliminary- 

 investigation s into the sequence of horizons in the Upper Lias of 

 various areas, in the Junction -Bed, and in the pre- Junction-Bed 

 strata of Thorncorube Beacon. A theory of stratal repetition and 

 coalescence is discussed in regard to the Watton Bed. Its main 

 date is taken to be Yeovilian, Hammatoceras hemera. The white 

 lithographic bed of Burton Bradstock is cited as evidence of stratal 

 repetition, and a theory as to the deposition and partial destruction 

 of this Burton bed is put forward. 



The Watton and JEmrton lithographic beds are cited as evidence 

 of Alpenkalk conditions prevailing in Western Europe during two 

 well-separated Jurassic dates, both of them far earlier than the 

 times of Alpenkalk deposits in Central and Eastern Europe. 



Certain remarks are made upon sections at Milborne Wick and 

 Haselbury (Somerset) in regard to the dating of their deposits, 

 and a table of the succession and distribution of Hammatoceratids 

 is given. 



A palseontological note describes a new species of Rhyncho- 

 nellid — a species marking a particular deposit at Thorncombe 

 Beacon. 



- Appendix I, by Mr. James E. Jackson, gives the result of his 

 studies of various sections of the Junction-Bed. 



Appendix IT, by Dr. L. F. Spath, Mr. J. Pringle, Mr. A. Temple- 

 man, and Mr. Buckman, deals wfth the Upper Liassic sequence, 

 with especial reference to facts disclosed by recent excavations at 

 Barrington ( Somerset) . 



2. •' Banded Precipitates of Yivianite in a Saskatchewan Eire- 

 clay.' By John Stansfield, B.A., F.G.S. 



A pale-grey Tertiary fire-clay worked for fire-bricks at Clay 

 Bank (Saskatchewan) contains bluish-black spherical, ellipsoidal, 

 and cylindrical patches varying from g- inch to an inch and a half 

 in greatest dimension. The central portions of the spheres, and the 

 long axes of the cylinders are deeply coloured, and are usually sur- 

 rounded by a uniformly stained area or by several concentric 

 stained layers of varying, but less intense, tint. The colour is due 

 to an earthy amorphous variety of vivianite, formed presumably by 

 precipitation. The precipitation has been brought about by dilute 

 iron -solutions reacting on solutions of phosphates of organic origin, 

 such solutions being brought together by diffusion through the 

 colloidal matter of the clay. The spacing of the vivianite -bands 

 is irregular, and appears to follow no known law ; but similar bands 

 of precipitation may be produced in gelatine by the reaction of 

 certain soluble salts one on the other. 



A small specimen of plattnerite (lead dioxide), a very rare 

 mineral recently rediscovered at Leadhills (Lanarkshire), was 

 exhibited by W.* Campbell Smith, M.C., M.A„ Sec.G.S. 



