1684 THE VOYAGE OF H.M.S. CHALLENGER. 



6. Castanella channeri, n. sp. 



Pores irregular, roundish, two to four times as broad as the bars. Bristles nearly half as long 

 as the radius. Mouth with seven to nine short conical teeth, shorter than the bristles, but much 

 thicker. 



Dimensions. — Diameter of the shell 0'3 to 0'4, of the pores 0'02 to 0'025. 



Hahitat. — North Atlantic, Stations 352 to 354, surface. 



7. Castanella horstoni, n. sp. 



Pores irregular, polygonal, three to four times as broad as the bars. Bristles about as long as the 

 radius. Mouth with si.x stout pyramidal teeth, which are scarcely one-third as long as the radius. 

 Dimensions. — Diameter of the shell 0"55, of the pores 0'02 to 0"025. 

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



Genus 707. Castanidium} Haeckel, 1879, Sitzungsb. med.-nat. Gesellscli. 



Jena, Dec. 12, p. 5. 



Definition. — C a s t a n e 11 i d a, with simple radial main-spines and a simple smooth 

 mouth. 



The genus Castanidium agrees with its ancestral form Castanarium in the simple 

 shape of the smooth and toothless mouth, but differs from it in the possession of long 

 radial main-sjiines, which are scattered between the constant radial bristles or by-spines 

 of the surface. The shell agrees therefore in its general shape with the Astrosphseride 

 Heliosphcera, as defined above (p. 217, PI. 26, fig. 9), but differs from it in the pos- 

 session of the shell -mouth wanting in all S p h £e r o i d e a. 



1. Castanidiwn ivillemoesi, u. sp. 



Pores regular, circular, hexagonally framed, twice as broad as the bars. Bristles three times 

 as long as the diameter of one pore. Eadial main-spines straight, conical, smooth, as long as the 

 radius. 



Dimensions. — Diameter of the shell 0"3 to 0'4, of the pores 0-012 to 0'016. 



Hahitat. — Central Pacific, Station 263 to 274, surface. 



2, Castanidium wildi, n. sp. 



Pores regular, circular, hexagonally framed, of the same breadth as the bars. Bristles twice as 

 long as one pore. Eadial main-spines straight and short, cylindrical, with dimpled surface (as in 

 PI. 113, fig. 1), as broad as one pore and as long as the diameter of the shell. 



Dimensions. — Diameter of the shell 0*66, of the pores 0'045. 



Hahitat. — South Pacific, Station 297, surface. 



1 Casto»itdmTO = Small chestnut ; xaarxvilion. 



