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



3. TrochodisGus odontotrochus, n. sp. 



Disk with smooth surface, in the distal part radially sulcated. Pores irregular, roundish ; twelve 

 to fourteen on the radius. Marginal spines very short and numerous (thuty to forty), conical, 

 scarcely one-fourth as long as the radius of the disk, which resembles a wheel with marginal teeth. 



Dimensions. — Diameter of the disk 0"18, of the pores 0'004; length of the spines 0'02, basal 

 breadth O'Ol. 



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



4. Troclwdiscus sokiris, n. sp. 



Disk with smooth surface. Pores subregular, circular ; eight to nine on the radius. Marginal 

 spines very numerous (sixty to eighty), in two to four girdles densely crowded together, the largest 

 as long as the diameter of the disk, bent and conical. (Similar to Heliodiscus Solaris, PI. 34, fig. 4, 

 Ijut without medullary shell.) 



Dimensions. — Diameter of the disk 0'15, of the pores O'OOS ; length of the spines 0*05 to 0'15, 

 basal breadth 001. 



Habitat. — South Pacific, Station 300, depth 1375 fathoms. 



5. Trochodiscus echiniscus, n. sp. 



Disk with spiny surface. Pores irregular, roundish ; ten to eleven on the radius. Marginal 

 spines conical, very numerous (forty to fifty), irregular in size and disposition, the largest half as 

 long as the radius of the disk. (Similar to Heliodiscus echiniscus, PI. 34, fig. 5, but without 

 medullary shell.) 



Dimensions. — Diameter of the disk 0"18, of the pores 0'005 to 0'015 ; length of the spines 0'02 to 

 0-04, basal breadth 0-01. 



Habitat. — North Atlantic, Fteroe Channel, John Murray. 



Subgenus 2. Pristodiscus, Haeckel. 



Definition. — Bases of the marginal spines connected by a solid siliceous equatorial 

 pirdle. 



6. Trochodiscus stellaris, u. sp. (PI. 48, fig. 3). 



Disk with smooth surface. Pores subregular, circular ; seven to eight on the radius. Marginal 

 spines twelve to sixteen, triangular, of subregular size and disposition, about half as long as the 

 radius of the disk, connected at their broad base by a solid equatorial girdle of half the breadth ; 

 girdle and spines radially striped. 



Dimc7isions. — Diameter of the disk 0-25, of the pores 0'015 ; length of the spines 0'04 to 0'06, 

 basal breadth 0-02 to 0-04. 



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



