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



1. Doracantha dorataspis, n. sp. 



Spines compressed, two-edged, tapering from the broader middle towards the two ends. Apex 

 simple. Base pyramidal, without leaf-cross. From the middle part of each spine arise two opposite 

 forked apophyses ; the neighbouring fork -branches are recurved and united in the tangential plane ; 

 so that each spine bears a plate or shield with two elliptical pores ; the margin of the roundish 

 plate bears a variable number of short teeth. 



Dimensions. Length of the spines 0'2, breadth O02. 



Habitat. Central Pacific, Station 271, surface. 



Genus 329. Astrolonche, 1 Haeckel, 1881, Prodromus, p. 465. 



Definition. A strolonchida with numerous simple apophyses (four to ei^ht or 

 _ more on each radial spine), which are arranged in two opposite longitudinal rows (rarely 

 in six such rows, opposite in three parallel planes). 



The genus Astrolonche differs from the preceding Phractacanthida in the multipli- 

 cation of the simple apophyses. Commonly these are opposite in pairs in two 

 longitudinal rows (on the two edges of the compressed spine, at least two on each side). 

 But sometimes (in the subgenus Astrolonchidium) there are six instead of two longitu- 

 dinal rows of teeth, and these are placed in three parallel planes. 



Subgenus 1. Astroloncharium, Haeckel. 



Definition. Each spine with two longitudinal rows of apophyses, opposite in one 

 meridian plane. 



1. Astrolonche bicruciata, n. sp. 



Spines compressed, two-edged, almost of equal breadth throughout their whole length, with 

 simple apex and small leaf -cross at the base. From the two edges of the middle part of each 

 spine arise two pairs of opposite apophyses, which are compressed and a little curved (convex on 

 the distal, concave on the proximal margin). All four apophyses are of the same size and form ; 

 the radial distance of each pair much smaller than their common distance from the centre. 



Dimensions. Length of the spines 0'25, breadth 0'02. 



Habitat. Central Pacific, Station 270, surface. 



2. Astrolonche mucronata, Haeckel. 



Acanthometra mucronata, J. Miiller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 49,Taf. x. fig. <J. 

 Aspidomma mucronatum, Haeckel, 1862, Monogr. d. Kadiol., p. 424. 



Spines conical, little compressed, with simple apex and small leaf-cross at the base. From tL" 

 basal half of each spine arise two pairs of opposite apophyses, which exhibit a very different fon.:. 



1 Astrolonche = Star-spear ; KO.JV, x> / ^. 



