REPORT ON THE RADIOLARIA. 557 



Subgenus 2. Pentalastromma, Haeckel. 



Definition Arms of different sizes, one odd arm larger than the two others ; the 

 opposite odd angle generally different from the four other angles. 



3. Pentalastrum ophidiaster, n. sp. (PI. 44, fig. 3). 



Arms nearly triangular, at their obtuse truncated distal end twice as broad as at their base. 

 Four arms equal, with five joints each ; the fifth arm twice as long, with seven joints. Angles 

 between the arms nearly equal ; the odd angle a little larger. 



Dimensions. Eadius of the larger odd arm 0'25, of the four smaller arms 0'15 ; basal breadth 

 0-035, distal breadth 0'07. 



Habitat. Pacific, central area, Station 274, surface. 



4. Pentalastrum cometa, n. sp. 



Arms nearly cylindrical, at their obtuse truncated distal end one and a .half times as broad as 

 at their base. Posterior odd arm very large, with eleven joints, about three times as long as the two 

 lateral arms (with five joints each) and four times as long as the two anterior arms (with three joints 

 each). Angles between the paired arms different; the two lateral angles smaller than the two 

 posterior, and these smaller than the odd anterior angle. 



Dimensions. Eadius of the odd posterior arm 0'5, of the lateral arms 0'25, of the anterior arms 

 0-18 ; basal breadth O'Oo, distal breadth 0'08. 



Habitat. South Pacific, Station 288, surface. 



Genus 241. Pentinastrum, 1 Haeckel, 1881, Prodromus, p. 461. 



Definition. P or o disci da with five simple, undivided, chambered arms, 

 connected by a patagium. 



The genus Pentinastrum differs from the foregoing Pentalastrum only in the 

 development of a patagium or connecticulum between the arms, and bears therefore 

 the same relation to it that Histriastrum does to Stauralastrum, or Hymeniastrum 

 to Dictyastrum. 



1. Pentinastrum asteriscus, n. sp. (PI. 44, fig. 2). 



All arms equal, twice as long as broad, at their base two-thirds as broad as at their truncated 

 distal end, which bears a strong, pyramidal, terminal spine. Each arm is divided by five transverse 

 septa into six joints or chambers, and each of these by a radial beam into a. pair of chambers. The 

 five radial beams arise from the innermost chamber of the central disk, and end in the five terminal 



1 Pentinastrum = Stamilet with five rays ; irim, i'yns, oiaryiv. 



