By A. J. Jukes-Browne, B.A., F.G.S. 



237 



separated by layers of hard green-coated nodules, and no one who 

 has once seen it would mistake it for any other bed in the Chalk, 

 So also, when a thin slice is viewed under the microscope, it is seen 

 to have a structure which is different from any other bed, aud Mr. 

 W. Hill, F.G.S. , writes that " no one who has seen a slide prepared 

 from this rock will mistake it for Chalk from any other horizon." 

 It is simply crowded with Foraminifera and with broken fragments 

 of shell and other organic remains ; sponge spicules are common, 

 and there are large grains of Glauconite like those which occur in 

 the Greensand far below. 



Figs. 5 and 7 illustrate this structure : Fig. 5 is the reproduction 



X60 



Fig. 6.— Structure of Middle Chalk, engraved from a drawing by 

 F. Rutley, Esq., F.G.S. 



of a beautiful photograph by Mr. Freshwater, and shows very well 

 the number and variety of Foraminifera which sometimes appear in 

 a single slice. Fig. 7 is a woodcut by Mr. Cooper, from a drawing 

 made by Mr. F. Rutley, F.G.S., and exhibits still better the different 

 kinds of organisms which are often crowded into a small area of 

 Chalk rock. A sponge spicule cut transversely is seen at $, a 

 grain of glauconite at/, and a fragment of Echinoderm shell at g } 

 while the large object above this is a Foraminifer (Verneuittina). 



