REPORT ON THE RADIOLARIA. 441 



Subgenus 3. Heliosestomma, Haeckel. 



Definition. — Surface of the disk smooth, without radial spines. Bases of the 

 marginal spines connected by a solid equatorial girdle. 



10. Heliosestrum octangidum, n. sp. 



Disk with smooth surface, octagonal, twice as broad as the medullary shell. Pores regular, 

 circular ; nine to ten on the radius. Equatorial girdle narrow, radially striped, connecting the 

 points of the eight short, regularly disposed, marginal spines in such a manner that the whole shell 

 forms a regidar octagon with rectilinear sides. 



Dimensions. — Diameter of the disk Oil to 0-12, of the medullary shell 0-05 to 0-06 ; lengtli 

 of the sides of the octagon 0'06. 



Habitat. — Central Pacific, Station 268, depth 2900 fathoms. 



11. Heliosestrum octogonium, n. sp. 



Disk with smooth surface, octagonal, four times as broad as the medullary shell. Pores 

 irregular, roundish ; eight to nine on the radius. Equatorial girdle broad, smooth, connecting the 

 points of the eight short, triangular, flat marginal spines in such a manner that the wliole shell forms 

 a subregular octagon with concave, nearly equal sides. (Sometimes seven or nine spines instead of 

 eight are developed.) 



Dimensions. — Diameter of the disk OIG to 0'18, of the medullary shell 004 to 0'05 ; length of 

 the radial -spines 0'02 to 0'04, basal breadth 003. 



Habitat. — Central Pacific, Station 26G, depth 2750 fathoms. 



12. Heliosestrum craspedotum, n. sp. 



Haliomma Ivumboldti, var., Bury, 1862, Polycystins of Barbados, pi. viii fig. 4 (below). 



Disk with smooth surface, three times as broad as the medullary shell. Pores subregular, 

 circular ; ten to twelve on the radius. Eight marginal spines (sometimes seven or nine) triangular, 

 deeply sulcated, half as long and one-third as broad as the radius of the disk, connected by a 

 narrow, radially striped equatorial girdle. 



Dimensions. — Diameter of the disk 0'18, of the medullary shell 0-06 ; length of the radial 

 spines 005, basal breadth 0-03. 



Habitat. — Central Pacific, Stations 271 to 274, at various depths, also fossil in Barbados. 



Genus 192. Astrosestrum,^ Haeckel, 1881, Prodromus, p. 457. 



Definition. — P h a c o d i s c i d a with double medullary shell and with eight radial 

 spines on the margin of the disk (more or less regularly disposed, sometimes seven or 

 nine). 



' /lsiroses(ntm = Stellated sieve ; cLgt^ou, aiinT^oi/. 

 (ZOOL. CHALL. EXP. — PART XL. — 1885.) Rr 56 



