REPORT ON THE RADIOLARIA. 171 



Subfamily HEXASTYLIDA, 1 Haeckel, 1881, Prodromus, pp. 449, 450. 

 Definition. C ubosphserida with one single spherical lattice-shell. 



Genus 72. Hexastylus, 2 Haeckel, 1881, Prodromus, p. 450. 



Definition. C ubosphserida with one simple lattice-sphere and six simple spines 

 of equal size. 



The genus Hexalonche is the most simple form of all Cubosphserida, and may be 

 regarded as the common ancestral form of this family. It can be derived phylogeneti- 

 cally from Cenosphcera, by development of six radial spines on the surface of the simple 

 spherical lattice-shell. These six simple spines are of equal size and opposite in pairs ill 

 the three dimensive axes, corresponding to the three equal axes of a cubic crystal. 



Subgenus 1. Hexastylanthus, Haeckel. 



Definition. Pores regular or subregular, of nearly equal size and form ; surface of 

 the cortical shell smooth, without radial by-spines (other than the six main spines). 



1. Hexastylus jihcenaxonius, n. sp. (PL 21, fig. 3). 



Shell thin walled, with smooth surface. Pores subregular, hexagonal, five to six times as broad 

 as the bars ; nine to ten on the radius. Six spines triangular pyramidal, as long as the radius of 

 the shell, as broad at the base as one pore. 



Dimensions. Diameter of the shell 013, pores O'OOS to O'Ol, bars 0'0015 ; length of the spines 

 0-07, basal breadth O'OOS to 0'012. 



Habitat. Central Pacific, Station 272, depth 2600 fathoms. 



2. Hexastylus sapientum, n. sp. 



Shell thin walled, with smooth surface. Pores regular, hexagonal, eight to ten times as broad 

 as the bars ; six to seven on the radius. Six spines bristle-shaped, longer than the diameter of 

 the shell. (Lattice-work and spines similar to those of Heliosphcera actinota, Monogr. d. Piadiol., 

 Taf. ix. fig. 3.) 



Dimensions. Diameter of the shell 015, pores 0'016, bars 0'002 ; length of the spines 0'2, 

 breadth 0'002. 



Habitat. North Atlantic, Station 354, surface. 



1 Hexastylida= Cubosphaerida siruplicia = Monosph;erida hexacantha. 



2 Hexastylus = Shell with six styles ; i, <n-t>Aof. 



