190 THE VOYAGE OF H.M.S. CHALLENGER. 



Diviensions. — Diameter of the outer shell 013, of the inner 0'05 ; length of the spines 0'5 to 

 0-8 or more, breadth 0-02. 



-Habitat. — Central Pacific, Station 271, surface. 



Genus 77. Hexaloncharium} n. gen. 



Definition. — C u b o s p h se r i d a with two concentric lattice-spheres and six simple 

 spines of different sizes ; one opposite pair larger than the two others. 



The genus Hexaloncharium exhibits the same relation to its ancestral form, 

 Hexalonche, that Hexastylarium bears to Hexastylus. Two opposite spines of one 

 pair are larger than the four others, and correspond to the tliree axes of a quadratic 

 crystal. 



1. Hexaloncharium octahedrum, n. sp. 



Cortical shell smooth, three to four times as broad as the spherical medullary shell, each having 

 regular circular pores, twice to three times as broad as the bars. Form of the outer shell not a 

 sphere, but a regular octahedi'on, with eight congruent, equilateral triangular even faces. Two opposite 

 spines twice as long as the shell diameter, whilst the four others are scarcely equal to it. Basal 

 breadth of all six the same (three times as large as one pore) ; form, three-sided prismatic, with 

 cuspidate distal end. (Similai- to Hexalonche octahedra, PI. 22» ^g- ^> but distinct in the unequal 

 length of the spines.) 



Dimensions. — Diameter of the outer shell 016, inner 0-045 ; length of the major spine 0'3, 

 minor 012, basal breadth D'OS. 



Habitat. — South Atlantic, Station 332, depth 2200 fathoms. 



2. Hexaloncharium 2'>hilosophic.um, n. sp. 



Cortical shell spherical, covered with short conical by-spines, twice as broad as the medidlary 

 shell ; both with regular circidar pores tliree to four times as broad as the bars. Two major spines 

 cylindrical, with conical apex, three times as long as the four others, wliich are conical and about 

 as long as the shell radius ; basal breadth of all six the same (equal to one pore). Shnilar to 

 Hexalonche anaxir/tenis (PI. 25, fig. 5), but distinct in the enormous prolongation of two opposite 

 spines. 



Dimensions. — Diameter of the outer shell 012, inner O'OG; length of the two major spines 0'2, 

 of the four minor 0'06, basal breadth 0"02. 



Habitat. — Central Pacific, Station 267, depth 2700 fathoms. 



' Hexaloncharium = Shell with si.x spears; derivation from Hexalonclie. 



