212 STRUCTUKE OF THE EOEAMIXIFEEAL SHELL. [vol. Ixxvii, 



Fig. 9. Section of the Elfhills Limestone with included ' Saccammina.' 

 The test of the ' Saccamminas ' is replaced by greenish -yellow 

 quartz, shown as the dark outermost zone ; this is succeeded by a 

 zone of calcite-crystals, and the central area is occupied by quartz. 

 X 8. (See p. 195.) 



10. Section of ' Saccammina ' with the wall sharply defined by a lining 



of carbonaceous matrix ; the rest of the cavity is filled partly with 

 matrix, partly with calcite, Xl6. (See p. 194.) 



11. Similar to fig. 10. Xl6. 



12. Section of ' Saccammina ' showing the wall replaced by quartz, con- 



taining black granules ; next a zone of calcite with the points of 

 the crystals directed inwards, and finally quartz which completes 

 the infilling. Xl6. (See p. 195.) 



13. Similar to figs. 10 & 11. xl6. (See p. 194.) 



14. The shell is replaced by quartz, which includes particles of matrix ; 



quartz also has grown inwards as a mosaic which is bounded by 

 agate-like chalcedony. The remaining space in the middle ip 

 filled with calcite. Xl6. (See p. 195.) 



Discus sio]s^. 



Dr. E. L. Sherlock enquired whether the Author eould explain 

 the brown colour shown by the imperforate foraiiiinifera when 

 viewed under the microscope by transmitted hght. In thin 

 sections of limestones the imperforate foraminifera show a colour 

 that varies somewhat in different forms, and in some cases resembles 

 that of a flake of biotite similarly viewed. The discovery that 

 these shells are composed of calcite explaiiis the fact of their per- 

 sistence in some limestones, such as the raised coral-reefs of Fiji, 

 where the aragonite organisms have disappeared. The paper was 

 both interesting and valuable. 



Dr. Stais'ley Smith remarked that in Northumberland, the tj-pe- 

 localit}" of Saccammina, that foraminifer is to be found in several 

 limestones as isolated specimens ; but it forms two very con- 

 spicuous bands — one, in the south of the count}' in the Four- 

 Fathom Limestone, the other in the north of the county in the 

 Acre Limestone, which lies immediatel}^ below the Four-Fathom 

 Limestone. The bands var}" up to 3 feet in thickness, and in the 

 northern area the matrix in which Saccammina is embedded 

 has often perished to a great extent, so that the bands bear some 

 resemblance to a thick layer of fossil wheat, as exposed in weathered 

 sections. 



The Author thanked those present for the manner in which 

 his communication had been received. 



