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



3. Hexastylus thaletis, n. sp. (PI. 21, fig. 4). 



Shell thin walled, with smooth surface. Pores subregiilar, circular, hexagonally framed, some- 

 what funnel-shaped, of the same breadth as the bars ; eight to nine on the radius. Si.x spines 

 triangular pyramidal, with prominent edges, as long as the radius, three to four times as broad at the 

 base as one pore. 



Dimensions. — Diameter of the shell Ol, pores and bars 0'005; length of the spines 0'05, basal 

 breadth 0-02. 



HaUtat. — Tropical Pacific, Station 225, depth 4575 fathoms. 



4. Hexastylus favosus, n. sp. 



Shell thick walled, with smooth surface. Pores regular, circular, hexagonally framed, deep 

 funnel-shaped, of the same breadth as the bars ; six to seven on the radius. Six spines triangiilar 

 pyi-amidal, as long as the diameter, twice as broad at the base as one pore. 



Bivicnsions. — Diameter of the shell 012, pores and bars O'Ol ; length of the spines 012, basal 

 breadth 0-02. 



Habitat. — South Atlantic, Station .320, surface. 



5. Hexastylus longissimus, n. sp. 



Shell thick walled, with smooth surface. Pores regular, circular, hexagonally framed, of the 

 same breadth as the bars ; five to six on the radius. Six spines triangular prismatic, extremely 

 elongated, ten to twenty times as long as the diameter of the shell, twice as broad as one pore. 



Dimensions. — Diameter of the shell 0'08, pores and bars O'OOS ; length of the spines I'O to 1-5, 

 breadth 0-015. 



Habitat. — Tropical Atlantic, Station 347, surface. 



6. Hexastylus minimus, n. .sp. (PI. 21, fig. 5). 



Shell thin walled, with smooth surface. Pores subregular, circular, twice as broad as the bars ; 

 five to six on the radius. Six spines triangular pyramidal, scarcely as long as the radius, at the 

 base half as broad as long. 



Dimensions. — Diameter of the shell 0-05, pores 0-004, bars 0-002 ; length of the spines 0-02, 

 basal breadth 0-01. 



Habitat. — Tropical Pacific, Station 225, depth 4575 fathoms. 



7. Hexastylus biantis, n. sp. 



Shell thin walled, smooth. Pores regular, circular, four times as broad as the bars ; eight 

 to nine on the radius. Six spines conical, as long as the radius, at the base as broad as 

 one pore. 



