REPORT ON THE RADIOLARIA. 451 



We can distinguish two subgenera : in Ildiodadas the surface of the disk is smooth, 

 in Heliodendrum covered with bristle-shaped radial spines, which are either simple or 

 also branched, sometimes longer than the thick marginal spines. 



Subgenus 1. Hcliocladus, Haeckel, 1881, Prodromus, p. 457. 

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



1. Heliodrymus dendrocyclns, n. sp. (PI. 33, fig. 9). 



Heliocladus dendroci/cliis, Haeckel, 1881, Prodromus et Atlas (pi. xxxiii. fig. 9). 



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

 hexagonally framed ; eight to nine on the radius. IMarginal spines sixteen to twenty, cylindrical, 

 very strong, flexuose, irregularly branched, nearly as long as the diameter of the disk. Between 

 these main spines, each of which bears two to six irregular branches, are scattered on the margin 

 numerous smaller simple spines. 



Dimensions. — Diameter of the disk OIG, of the medullary shell O'Oo ; length of the main spines 

 l)-l to 0-14, breadth 0-01 to 0-02. 



Habitat. — Central Pacific, Station 271, surface. 



2. Ileliodri/miis fttrcatu.s, n. sp. 



Disk with smooth surface, four times as broad as the medullary shell. Pores irregular, roundish ; 

 ten to twelve on the racUus. Marginal spines twenty to twenty-five, cylindrical, tiexuose, forked, 

 about as long as the radius of the dislc ; fork-branches irregular, of unequal size. Some smaller 

 simple spines are scattered between the forked ones. 



Dimensions — Diameter of the disk 015, of tlie medullary shell 0-04 ; length of the radial spines 

 0-07 to 0-09, breadth 0-01. 



Eahitat. — Central Pacific, Station 265, surface. 



'6. Heliodrymus grotiensis, Haeckel. 



Heliodiscus ijrottensis, Stohr, 1880, PaL-Bontogr., vol. xxvi. p. 89, Taf. i. fig. 13. 



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

 roundish ; eight to nine on the radius. Marginal spines twenty to thirty, conical, very irregular in 

 form, size, and disposition ; the smaller simple, the larger irregularly branched and half as long as 

 the radius of the disk. 



Dimensions. — Diameter of the disk 0'17, of the medullary shell 0'07 ; lengtli of the marginal 

 spines 002 to 0-04, basal breadth O'Ol to 0-02. 



HeMtat. — Fossil in Tertiary ro^ks of Sicily, Grotte, Stohr. 



