1682 THE VOYAGE OF H.M.S. CHALLENGER. 



2. Castanarium hookeri, n. sp. 



Pores regular, circular, hexagoually framed, twice as broad as the bars. Eadial bristles one- 

 third as long as the radius. 



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

 Habitat. — Indian Ocean, Cocos Islands (Eabbe), surface. 



3. Castanarium lyelli, n. sp. 



Pores regular, circular, without hexagonal frames, of the same breadth as the bars. Eadial 

 bristles twice as long as the diameter of one pore. 



Dimensions. — Diameter of the shell 0'24, of the pores 0'015. 

 Habitat. — Central Pacific, Station 272, depth 2600 fathoms. 



4. Castanarium lubbochi, n. sp. 



Pores irregularly roundish, about of the same breadth as the roundish, non-crested bars. Eadial 

 Ijristles one-third as long as the radius. 



Divie7isio7is. — Diameter of the shell 0'36, of the pores 0"01 to 0^02. 

 Habitat. — Tropical Atlantic, Station 348, depth 2450 fathoms. 



5. Castanarium huxleyi, n. sp. 



Pores irregularly polygonal, two to three times as broad as the bars, separated by prominent 

 polygonal crests. Eadial bristles half as long as the radius. 



Dimensions. — Diameter of the shell 0'45, of the pores 0'02 to 0'05. 

 Habitat. — South Pacific (off Australia), Station 165, surface. 



Genus 706. Castanella,^ Haeckel, 1879, Sitzungsb. med.-uat. Gesellsch. 



Jena, Dec. 12, p. 5. 



Definition. — C astanellida without radial main-spines, with a dentate mouth. 



The genus Castanella comprises the most common and most widely distributed 

 species of Castanellida. It agrees in general shape with its ancestral form, the 

 preceding Castanarium, differing from it only in the possession of strong teeth, which 

 form a corona around the mouth. 



1 GastaTvella = Diminutive of Gastanea. 



