440 THE VOYAGE OF H.M.S. CHALLENGER. 



seven or uiue) conical, half as long as the radius, twice as long as broad, without a connecting 

 equatorial girdle. 



Dimensions. — Diameter of the disk 017, of the medullary shell 0'04; length of the radial spines 

 0-04, basal breadth 0-02. 



Hahitat. — Fossil in Barbados. 



7. Heliosestrum irreyuJan', ii. sp. 



Disk with smooth surface, four tunes as broad as the medullary shell. Pores irregular, 

 roundish ; nine to eleven on the radius. Eiglit conical radial spines of in-egular size and distribution, 

 often seven or nine, about as long as the radius of the disk (in some cases longer, in others shorter). 

 No connecting equatorial girdle. 



Dimensions. — Diameter of the disk 0'2, of the medullary shell 0"05 ; length of the radial spines 

 01, basal breadth 0-02. 



Habitat. — Central Pacific, Stations 270 to 272, depth 2425 to 2925 fathoms. 



Subgeuiis 2. HeUosestiUa, Haeckel. 



Definition. — Surface of the disk armed with radial spines. Bases of the marginal 

 spines free, without a connecting equatorial girdle. 



8. Heliosestrum octonmn, n. sp. (PL 34, fig. 3). 



Disk with sjiiny surface, three times as broad as the medullary shell. Pores circular, of very 

 different sizes ; eight to ten on the rachus. Eight conical marginal spines of equal size and equi- 

 distant, as long as the radius of the disk, and one-third as liroad at the base as the medullary shell. 

 Numerous spines on the surface bristle-shaped, on the margin half as long as the eight main spines, 

 in the central part shorter. 



Dimensions. — Diameter of the disk 0'18, of the medullary shell (VOli ; length of the marginal 

 spines 01, basal breadth 0'02. 



Habitat. — Central Pacific, Station 271, surface. 



9. Heliosestrum. cegineta, n. sp. 



Disk with spiny surface, four tunes as broad as the medullary shell. Pores irregular, roundish, 

 of different sizes ; twelve to fourteen on the radius. Eight pyramidal marginal spines regularly 

 disposed, four larger (perradial) alternating with four smaller (iuterradial) ; the former as long as 

 the radius of the disk, the latter half as long. 



Dimensions. — Diameter of the disk 0'2, of the medullar)- shell 0'05 ; length of the marginal 

 .spines 0-05 to 01, basal breadth O'Do. 



Habitat. — South Atlantic. Station 330, surface. 



