REPORT ON THE RADIOLARIA. 559 



2. Pentophiastrum caudatum, n. sp. (PI. 47, fig. 5). 



Arms in pairs different ; four arms in the basal half simple, in the distal half forked ; the 

 fifth (posterior) odd arm simple, undivided, cylindrical ; the anterior pair a little smaller than the 

 posterior ; the neighbouring branches of the two pairs on each side larger than the two others. 

 Axes of the arms and their branches straight. 



Dimensions. Radius of the arms about - 5, breadth 0'12. 



Habitat. North Atlantic, Station 353, depth 2965 fathoms. 



3. Pentophiastrum for cipatum, n. sp. (PI. 47, fig. 4). 



Arms in pairs different, all in the basal two thirds simple, in the distal third forked. Only in 

 the posterior (odd) arm both branches are equal, in the four others unequal. The common axis of 

 the posterior lateral pair is horizontal, perpendicular to the median line ; the axes of the anterior 

 pair are pincer-like, concavely curved towards the median line or principal axis. 



Dimensions. Eadius of the arms about 0'5, breadth O14. 



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



Genus 243. Hexalastrum, 1 Haeckel, 1881, Prodromus, p. 461. 

 Definition. P orodiscida with six simple chambered arms, without a patagium. 



The genus Hexalastrum, together with the following Hexinastrum, encloses those 

 Euchitonida in which the number of the chambered arms surrounding the central disk 

 amounts to six. This is the highest number of these articulated marginal appendages 

 which is reached in any Discoidea. Formerly (1881) in my Prodromus, p. 459, I 

 supposed that the same number was reached also by one Coccodiscid, and called this 

 genus Ilexactura. Afterwards I was convinced that this form was also a Hexalastrum. 



1. Hexalastrum palmanthum, n. sp. 



All six arms equal, with equal angles between them. Each arm club-shaped, three times as 

 long as broad, twice as broad at the thickened distal end as at the base, without a terminal spine. 

 Dimensions. Eadius of each arm 0'2, basal breadth 0'02, distal breadth 0'06. 

 Habitat. Pacific, central area, Station 274, depth 2750 fathoms. 



2. Hexalastrum crinanthum, n. sp. 



All six arms equal, with equal angles between them. Each arm club-shaped, four times as long 

 as broad, at the egg-shaped distal end three times as broad as in the linear basal part, provided 



1 Hexalastrum = Little sea-star with six rays ; i%a, &\;, aarjov. 



