608 THE OCCURRENCE OF RADIOLARIA IN CHALK. [Nov. 1895, 



Locality : Eoyston. Horizon : Melbourn Eock. 



PL XXII. fig. 14 shows a well-marked circular outline, the walls 

 of the test still faintly indicated, and filled with finely granular 

 crystalline calcite. No medullary shell. A single spine, thin at its 

 base, but clubbed at its distal end. 



Diameter "36 mm. Length of spine *27 mm. 



Locality : Eoyston. Horizon : Melbourn Rock. 



The following form is probably imperfect : — 



PL XXII. fig. 13. In section a circle filled with clear, fine granular 

 calcite. No medullary shell. A single primary radial spine, strong, 

 and markedly twisted. There is no evidence of other spines, primary 

 or secondary. 



Diameter '18 mm. Length of spine -25 mm. 



Locality ; Wilbury Hill, Hitchin. Horizon : Melbourn Eock. 



These are the more striking figures which we recognize as radio- 

 larians of the Chalk ; we do not think that the list is by any means 

 exhausted. Many other forms exist in our slides, the outlines of 

 which may possibly indicate other families and species, which further 

 study may enable us to identify ; we have only described those of 

 whose identity we have little doubt. 



Plate XXII. 

 Microscope-sections of radiolaria from the Melbourn Eock. 



Discussion. 



Dr. G. J. Hinde said that the discovery of radiolaria for the first 

 time in the English Chalk, as distinguished from their occurrence in 

 Chalk-flints, was an interesting fact. One might naturally have 

 expected that some would be present in association with the 

 foraminiferal deposits of the Chalk, but they had hitherto eluded 

 observation, probably owing to the fact that, in common with other 

 siliceous organisms in beds mainly calcareous, their structures were 

 dissolved and only casts now remained, which without careful 

 scrutiny might be passed over as those of foraminifera. He had 

 seen the Authors' sections, and could corroborate their conclusions. 

 The Authors had also done good service in describing the various 

 phases of the fossilization of radiolaria in the calcareo-siliceous 

 beds of Barbados and comparing them with those of the Chalk of 

 this country. 



Prof. T. Rupert Jones stated that, in the Trans. Hertfordshire 

 Nat. Hist. Soc. vol. iii. (1885) p. 152, he had referred to the dis- 

 covery of PolycystincB in the Chalk, — namely, Astromma, Haliomma, 

 Podocyrtis, and some of the allied Dictyochidce, by Dr. Wallich, in 

 1883. Some were found in solid flint, and some in flint-meal from 

 hollow flints, from Surrey and elsewhere. 



Mr. W. Hill regretted that the communication of Prof. E. Jones 

 to the Herts. Nat. Hist. Soc. should have been overlooked. He 

 thanked the Society for their reception of the paper. 



