REPORT ON THE RADIOLARIA. 201 



Subfamily Hexaceomyida,^ Haeckel, 1881, Prodromus, pja. 449, 453. 

 Definition. — C u b o 8 p li ib r i d a with four concentie splierical lattice-shells. 



Geuus 82. Hexacromyvm,'^ Haeckel, 1881, Piodromus, p. 453. 



Definition. — C u 1) o s p h a? r i d a with four concentric lattice-spheres and six simple 

 spines of equal size. 



The genus Hexacromyum possesses four concentric, spherical, or octahedi'al lattice- 

 shells ; two inner medullary shells within the central capsule, two outer cortical outside 

 it. The four spheres are connected by six radial beams, which are prolonged outside into 

 simple spines of equal size, opposite in pairs in the three dimensive axes. This genus 

 can be derived from Hexacontium by duplication of the cortical shell. 



1. Hexacromyum elegans, n. sp. (PI. 24, fig. 9). 



SheU composed of four concentric shells, with radial proportions 1 : 2'5 : 7'5 : 10. Pirst 

 (innermost) shell with very small circular pores, second shell with larger circular pores. Third 

 shell (inner cortical shell) with large, subregular, circular, hexagonally framed pores (eight to lune 

 on the radius), twice as broad as the bars ; from the elevated nodal-points of the hexagonal frames 

 (between every three pores) arise thin bristle-shaped radial beams, which are united at the distal 

 end by vaulted branches forming the delicate fourth shell. Surface smooth. Eadial spines three- 

 sided pyramidal, as long as the radius, as broad at the base as the innermost sheU. 



Dimensions. — Diameter of the four shells— (A) 0-02, (B) 0-05, (C) ()-15, (D) 0-2 ; length of the 

 six radial spines 01, basal breadth 0^02. 



Habitat. — Central Pacific, Station 271, surface. 



2. Hexacromyum quadrigatum, n. sp. 



Shell composed of four concentric shells, with radial proportion =1 :3 :8 : 10. Structure of all 

 four shells the same, with regular, circular pores, twice to three times as broad as the bars; size of 

 the pores gradually increasing from the innermost to the outermost shell ; surface smooth. Eadial 

 spines three-sided pyramidal, as long as the radius, half as broad at the base as the innermost 

 shell. 



Dimensions. — Diameter of the four shells— (A) 0-025, (B) 0-08, (C) 0-20, (D) 0-25 ; length of the 

 spines 0'12, basal breadth 0-012. 



Hahitat, — North Pacific, Station 253, depth 3125 fathoms. 



' Hexacromjada = CubosphEerida quadruplicia = Tetraspliarida hexacantha. 

 2 He.xacroiiiyum = Om.ori witli six rays ; f|«, K^ofivov. 

 (ZOOL. CHALL. EXP. — PART XL.— 1885.) R'- 26 



