Vol. 55.] PKOM CHTPONS FARM, MULLION PARISH. 215 



indicated by the dark material of the groundmass, while the 

 interior of the tests has been infilled with clear silica, sometimes 

 cryptocrystalline, at others of fibrous chalcedony. IS'ot infrequently, 

 the opaque material in the groundmass has taken the place of the 

 clear silica in the hollow of the test, and the organism then 

 appears as a small circular or oval blot in the section. In the 

 forms showing the structural details, these alone have been replaced 

 by the opaque substance and are thus clearly defined against the 

 clear silica infilling the test. The radiolaria so favourably 

 preserved are, unfortunately, restricted to very small portions of 

 the rock, and in a microscopic section of the chert we may find a 

 group of the organisms in one corner of the slide with spines and 

 lattice-mesh nearly complete, while the rest of the slide contains 

 only stractureless forms. 



II. Description^ of the Radiolaria. 



Class RADIOLARIA, Miiller. 



Subclass SFU3IELLARIA, Ehrenberg. 

 Order SPHiEROIDEA, Haeckel. 

 Genus Stiomosph^ra, Haeckel. 



The test is a simple hollow latticed sphere, with radial rods ex- 

 tending from the centre to the inner surface of the wall. 



Stigmosph^ra echinata, sp. nov. (PI. XYI, fig. 1.) 



Test small, with a very delicate lattice-mesh and minute sub- 

 equal rounded pores. Here and there are small conical surface- 

 spines. The interior rods are now partially broken and displaced. 

 Diameter of test, 0-1 mm. ; of the pores, 0*005 mm. ; length of 

 surface-spines, 0*015 mm. Rare. 



Genus CARPOSPHiERA, Haeckel. 



The test consists of two concentric latticed spheres connected by 

 radial bars. 



Carposph^ra nana, sp. nov. (PI. XVI, fig. 2.) 



Test small, with delicate mesh and minute rounded pores. Only 

 the outline of the inner sphere is shown ; it is connected with the 

 cortical test by five or six short bars. Diameter of test, 0*065 mm. ; 

 of the inner sphere, 0*03 mm. A somewhat larger, but otherwise 

 very similar form, occurs in the chert from MuUion Island, which 

 might be included in this species.^ 



1 Quart. Journ. Geol. Soc. vol. xHx (1893) p. 217 & pi. iv, fig. 3. 



