77(3 THE VOYAGE OF H.M.S. CHALLENGER. 



than the frontal spine. Eight tropical spines different, the four anterior (hi, hi, ill, di) suiaUer, with 

 longer horns ; the four posterior (&2, &3, cl'2, d3) broader, with shorter horns ; the anterior horn of each 

 tropical spine is longer than-the posterior. Eight polar spines rudimentary, simple, very short. 



Dimensions. — Lengtli of the equatorial spine-cross 0'6, breadth 0'4. 



Habitat. — Central racific. Station 271, surface. 



Subfamily 2. Lithopterida, Haeckel. 



Definition. — Q u a d r i 1 o n c h i d a with two opposite transverse apophyses either 

 oil all twenty spines or only on a part of them. 



Genus 338. Quadrilonche,^ n. gen. 



Definition. — Q u adr i loncli i d a with two simple opposite apophyses either on 

 each radial spine or only on a part of the twenty spines. 



The genus Quadrilonche is the ancestral form of the Lithopterida, or of those 

 Quadrilonchida which bear two opposite apophyses or transverse processes. In 

 Quadrilonche these apophyses are simple, whilst they are branched in Xiphoptera and 

 fenestrated in Litlioptera. Each of these three genera may be divided into three sub- 

 genera ; ill the first only the four equatorial spines are provided with apophyses, in the 

 second twelve spines (four equatorial and eight tropical), in the third subgenus all 

 twenty spines. 



Subgenus 1. Quad riloncharium, Haeckel. 



Definition. — Four large equatorial spines provided with transverse apophyses; sixteen 

 other smaller spines simple, without apophyses. 



1. Quadrilo7iche tetrastaura, n. sp. 



Four equatorial spines very large, compressed, two-edged, each crossed in the distal third Ijy two 

 opposite simple apophyses. Sixteen other spines also compressed, linear, somewhat shorter than the 

 former and only half as broad, without apophyses. 



Dimensions. — Length of the four major spines 012, breadth 0-02 ; length of the sixteen minor 

 spines 0-08, breadth 0-01. 



Hahitat. — Central Pacific, Station 266, surface. 



1 Q«ac?ri/o)!(;/ie = Square-jpear. 



