REPORT ON THE RADIOLARIA. 429 



Subgenus 2. Heliostylus, Haeckel, 1881, Prodromus, p. 457. 



Definition. — Margin of the disk with a solid equatorial girdle or a corona of radial 

 spines. 



3. Sethostyhcs dentatus, n. sp. (PL 34, fig. 1). 



Heliostylus deiitatus, Haeckel, 1881, Prodromus et Atlas (pi. xxxiv. fig. 1). 



Disk with smooth surface, six times as broad as the medullary shell. Pores regular, circular ; 

 eighteen to twenty on the radius of the disk. Margin of the disk with a broad solid equatorial girdle, 

 which bears fifty to sixty strong conical teeth on the periphery; teeth about as long as the diameter 

 of the medullary shell. Both opposite marginal spines cyHndro-conical, about as long as the diameter 

 of the disk, and as broad as the girdle. 



Dimensions. — Diameter of the disk 0'3, of the medullary shell O^Oo ; length of both main spines 

 0-2 to 0-3, breadth 0-02. 



Hahitat. — Pacific, central area, Station 272, depth 2600 fathoma 



4. Sethostylus serratus, n. sp. (PL 34, fig. 2). 



Heliostylus serratus, Haeckel, 1881, Prodromus et Atlas (pi. xxxiv. fig. 2). 



Disk with smooth surface, four times as broad as the medullary shell. Pores regular, circular; 

 fouteen to sixteen on the radius of the disk. Margin with a broad solid equatorial girdle, which 

 bears forty to fifty strong conical teeth on the periphery ; teeth about as long as the radius of the 

 meduUary shell. Both ojjposite marginal spines spindle-shaped, about as long as the diameter of 

 the disk, and as broad as the girdle. 



Dime'nsions. — Diameter of the disk 0'3, of the medullary shell 0'075 ; length of both main 

 spines 0-2 to 0-3, breadth 0-03. 



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



5. Sethostylus hastatus, n. sp. 



Disk with smooth surface, two and a half times as broad as the medullary shell. Pores 

 irregular, roundish ; ten to twelve on the radius of the disk. Margin with a broad solid equatorial 

 girdle, which bears on the periphery six conical teeth, three on each half between the two main 

 spines, which are cylindrical, longer than the diameter of the disk, and half as broad as the girdle. 

 (This species can be derived from Helioscstrum, two opposite spines of the eight marginal spines 

 being much stronger developed than the other six.) 



Dimensions. — Diameter of the disk 0'15, of the medullary shell O^OG ; length of both main 

 spines 0-2, breadth 001. 



Habitat. — North Atlantic, Station 354, surface. 



