Vol. 56.] UrPER CHALK AT COULSDON. 695 



In addition to these, Dr. Riist also described, in 1892, 1 sixteen 

 species occurring in the shales of the Pierre Formation of North- 

 western Manitoba, belonging to the Upper Cretaceous ; of these, 

 thirteen were new species. 



During the discussion which followed the reading of Messrs. Hill 

 & Jukes-Browne's paper, Prof. T. Rupert Jones referred to the 

 discovery of Polycistina in the Chalk in 1883, which was published 

 in Trans. Herts Nat. Hist. Soc. vol. iii (1885) p. 152. 



The radiolaria described in the following pages were contained in 

 the cavities of two small flints which were thrown out of the new 

 railway-cutting between Coulsdon Station and the new Merstham 

 Tunnel on the London, Brighton, & South Coast liailway. The 

 exact horizon from which they were derived is difficult to determine, 

 but from the presence on the same heap of numbers of Holaster 

 planus, Micraster Leskei, and Terebratula carnea, it may fairly be 

 concluded that they came from the Holaster-planus zone. The 

 material from the cutting was removed by means of a tramway, and 

 deposited in enormous heaps by the side of the railway. The hollow 

 flints are fairly numerous : in many instances they have a solid 

 cylindrical core and are filled with a mealy substance, which is 

 contained in the cavity between the central core and the outer 

 coating. Caleb Evans 2 notes the occurrence of similar flints in the 

 Lower Kenley Beds. The mealy material inside, after being treated 

 with diluted hydrochloric acid, yielded, besides the radiolaria, large 

 numbers of the silicified casts of foraminifera in good preservation, 

 together with sponge-spicules belonging to the Monactinellidse, 

 Tetractinellidae, Lithistidse, and Hexactinellidge. Among the smaller 

 spicules may be noted the occurrence of a large inequianchorate of 

 an Esperia, *15 mm. in length. This mixture of organisms is such 

 as may often be found in recent deep-sea soundings. 



Although the external forms of the radiolaria from Coulsdon 

 are in most cases easily recognizable, the surface is very much 

 altered by corrosion, and their specific characters are in consequence 

 exceedingly difficult of determination. 3 So much is this the case, 

 that I have been obliged to content myself with the generic name 

 alone in most instances. This is especially true with regard to the 

 Discoidea : their internal structure cannot be discerned from an 

 external view, and the surface-markings on the fossils are frequently 

 due to secondary action. Again, the globate spicules of species of 

 Geodia so much resemble in outward appearance many of the 

 Sphaeroidea and Prunoidea, especially the forms of Cenosphcera, 

 ConospTicera, and Cenellipsis, that it will be more satisfactory not to 

 attempt their enumeration. The smaller forms of the Cyrtoidea 

 have been also omitted. 



1 Geol. Surv. Canad. 'Contrib. Canad. Micro-Palaeont.' pt. iv. 



2 ' On some Sections of Chalk between Croydon & Oxtead ' Proc. Geol. Assoc. 

 Suppl. to vol. i (1870) p. 15. 



3 The secondary markings due to corrosion are especially noticeable on some 

 of the sponge-spicules, which exhibit a regular series of pittings. 



