REPORT ON THE RADIOLARIA. 927 



3. Periplecta monocyrtis, n. sp. 



Spines of nearly equal size and shape, cylindrical, irregularly branched. The apical spine is 

 straight, more branched and nearly twice as long as the three basal spines. All four spines in the 

 basal third connected by a loose spongy framework, approaching the form of some Monocyrtida. 



Dimensions. Length of the apical spine 0'24, of the basal spines 0'13. 



Habitat. Central Pacific, Station 274, surface. 



Subfamily 3. HEXAPLECTIDA, Haeckel. 

 Definition. P lectanida with six radial spines. 



Genus 398. Hexaplecta^ Haeckel, 1881, Prodromus, p. 425. 



Definition. P lectanida with six radial spines, arising from one common central 

 point. 



The genus Hexaplecta has probably been derived from Hexaplagia by concrescence 

 of the meeting branches of the six spines, and therefore has to it the same relation 

 that Plectophora bears to Plagiacantha. The two species here described represent 

 perhaps two different genera, since in the first all six spines are equal, opposed in pairs, 

 in the second different in pairs (three upper smaller and three lower larger). 



1. Hexaplecta triaxonia, n. sp. 



Spines equal, opposite in three crossed pairs, straight, three-sided prismatic, thorny, in the 

 distal half with three leaf-shaped, dentate edges, in the basal half with three verticils of slender 

 branches, which are connected by parallel threads, and so form an arachnoidal network with rect- 

 angular or rhomboidal meshes. 



Dimensions. Length of the spines 0'22, of their basal branches 0'06. 



Habitat. South Pacific, Station 285, depth 2375 fathoms. 



2. Hexaplecta tricladonia, n. sp. 



Spines unequal, three larger spines (in the lower half of the body) being opposite to three 

 smaller spines (in the upper half). The latter are nearly horizontally expanded, each bearing three 

 straight divergent branches. The larger are stronger, twice as long and armed with three verticils, 

 each of three branches. All six spines are slender, three-sided prismatic. Their branches are very 

 thin, thread-shaped, and form by their union a loose network with irregular polygonal meshes. 



Dimensions. Length of the larger spines 0'25, of the smaller 0'12. 



Habitat. South Pacific, Station 291, surface. 



1 Hexaplecta = Hunting net with six beams ; %! 



