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



Subgenus 1. Staurentodiscus, Haeckel. 

 Definition. Internal cavity of the shell with centripetal axial rods. 



1. Crucidiscus endostaurus, n. sp. (PI. 48, fig. 2). 



Disk with smooth surface and smooth simple margin. Pores regular, circular ; thirteen to 

 fourteen on the radius of the disk. Four crossed spines conical, strong, longer than the radius of the 

 disk, on the inside prolonged into four thinner centripetal axial rods, which do not reach the centre. 

 In the middle part of the disk also some other short axial rods arise from the inside, not reaching 

 the centre (as in Stylodiscus endostylus, PI. 31, fig. 11). 



Dimensions. Diameter of the disk 0'16, of the pores 0'004 ; length of the spines 0'2, breadth 

 0-014. 



Habitat. North Pacific, Station 253, depth 3125 fathoms. 



Subgenus 2. Staurexodiscus, Haeckel. 

 Definition. Internal cavity of the shell without centripetal axial rods. 



2. Crucidiscus cuspidatus, n. sp. 



Disk with smooth surface and simple smooth margin. Pores regular, circular; seven to eight on 

 the radius of the disk. Four crossed spines pyramidal, with prominent edges, somewhat shorter 

 than the radius of the disk, twice as broad at their thick base as one pore. No internal axial 

 rods in the shell cavity. 



Dimensions. Diameter of the disk 012, of the pores 0'005 ; length of the spines O'Oo, basal 

 breadth 0'025. 



Habitat. Pacific, central area, Station 268, depth 2900 fathoms. 



3. Crucidiscus echinatus, n. sp. 



Disk with thorny surface and thorny margin. Pores regular, circular, six to seven on the 

 radius. Four crossed spines pyramidal (four-sided ?), about as long as the radius of the disk, as broad 

 at their base as one pore. No internal axial rods. Spines of the surface short, conical. 



Dimensions. Diameter of the disk 0'14, of the pores O'OOS ; length of the spines 0'08, basal 

 breadth 0'02. 



Habitat. Pacific, central area, .Station 2*71, depth 2425 fathoms. 



4. Crucidiscus cruciatus, n. sp. 



Disk with smooth surface and broad dentated margin. Pores regular, circular ; eleven to twelve 

 on the radius. Four crossed spines pyramidal, sulcated, about as long as the radius of the disk, as 



