OOLITE OF THE COTTKSWOLD RILLS. 559 



Section of the Ragstones, Chedworth Wood, 



ft. 



Cl//pcu!> Plotii Beds 8 



Grey Limestone 12 



Grjphite Grit 22 



42 



The Grj^phite Grit is crowded with the bivalve Gryphoea suhlobata, 

 embedded in a dark limestone. Thin sections of this under a 

 microscope show numerous well-preserved remains of polyzoa, of 

 shells and fragments of cchinodermata, with a quantity of calcite. 

 Polyzoa have evidenth' contributed largely to the limestone. 



Next in ascending order comes about 12 feet of grey limestone. 

 The top beds of this probably represent the so-called Upper Ti-ujonia 

 Grit of some geologists. Thin sections under a microscope show 

 it to be made up of a variet}' of organic fragments, including 

 foraminifera, ecliinodermata, ostracoda, portions of shells, and a 

 quantity of infilling calcite. There are also a few oolitic granules 

 present, in which tubules of Gh'vanella were noticed. 



Then come the Clypeus Plotii Beds. They consist for the most 

 part of a loose argillaceous oolite, in which are numerous specimens 

 of the sea-urchin, Chjpeus Plotii. The oolitic granules are large 

 and of organic origin, the tubules of (xirvaneUa being frequently 

 distinguishable. 



The Ragstones terminate the Inferior Oolite and are overlain by 

 the Fuller's Earth. 



Paet II. — Insoluble Residues. 

 (a) Details of Residues in the Beds referred to in Part I. 



The residues were obtained by treating some of the rock with 

 strong hydrochloric acid in a small flask. After the evolution of 

 carbon dioxide had ceased, the flask w^as placed on a tripod and the 

 contents boiled. This having been done, the residue was allowed to 

 subside ; the solution was then poured off, and the residue washed 

 three or four times with distilled water, and allowed to subside 

 after each M'ashing. It was next transferred to a platinum dish or 

 a watch-glass, and dried in a hot-air oven. When working on the 

 Oolite Marl and the argillaceous bed at the top of the Upper Free- 

 stone at Chedworth, a modification of this process was adopted, 

 which will be explained in a later portion of this paper. 



As far as possible I have taken the residues from the same beds 

 and in the same order that I have the thin section in Part I. 



The Transition Beds. — The specimens examined were collected 

 from No. 3 cutting east of Andoversford, on the Midland and South- 

 western Junction Ilailwav. A section of the beds is given on 

 p. 551. 



No. 1. This, the representative of the Midford Sands, yielded 88 

 per cent, of residue insoluble in hydrochloric acid. This insoluble 

 residue consisted chiefly of quartz, jagged flakes of mica, some zircon 

 and felspar. 



