1074 THE VOYAGE OF H.M.S. CHALLENGER. 



3. Dictyospyris biloba, n. sp. 



Shell subspherical, tuberculate, with slight sagittal stricture. Pores very numerous, small, 

 circular. No larger pores on either side of the ring. Basal plate with two very large circular 

 pores, surrounded by a circle of smaller pores. 



Dimensions. Shell 0'07 long, 0'08 broad. 



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



Subgenus 2. Dictyospyrella, Haeckel. 



Definition. Basal plate with three large collar pores (two paired posterior cardinal 

 pores and an odd anterior sternal pore). 



4. Dictyospyris triomma, n. sp. 



Shell nut-shaped, smooth, with deep sagittal stricture. Pores not numerous, large, polygonal 

 roundish, two pairs of very large annular pores on each side of the ring. Basal plate with three 

 large triangular pores. No free internal procolumella. 



Dimensions. Shell 0'06 long, 0'09 broad. 



Habitat. Indian Ocean, Zanzibar (Pullen), depth 2200 fathoms. 



5. Dictyospyris tristoma, Ehrenberg. 



Dictyospyris tristoma, Ehrenberg, 1875, Abhaudl. d. k. Akad. d. Wiss. Berlin, p. 70, Taf. xix. 

 fig. 9. 



Shell nut-shaped, tuberculate, with slight sagittal stricture. Pores numerous, irregular, roundish. 

 Three pairs of larger annular pores on each side of the ring. Basal plate with three large semi- 

 circular pores (the sternal odd pore apparently halved by an internal free procolumella). 



Dimensions. Shell 0'05 long, 0'08 broad. 



Habitat. Fossil in Barbados and Sicily (Caltanisetta). 



6. Dictyospyris triloba, Ehrenberg. 



Dictyospyris triloba, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 70, Taf. xix. fig. 8. 



Shell nut-shaped, spinulate, without external stricture, but with a complete internal sagittal 

 ring. Pores numerous, subregular circular ; no larger annular pores. Basal plate with three large, 

 heart-shaped two-lobed collar pores. 



Dimensions. Shell 0'05 long, 0'07 broad, 



Habitat. Fossil in Barbados. 



