364 THE VOYAGE OF H.M.S. CHALLENGED. 



4. Cyphonium trinacrium, n. sp. 



Cortical shell thick walled, with rough surface ; pores subregular, circular (without hexa- 

 gonal frame), not broader than the bars ; five to six on the half meridian of eacli chamber, 

 nine to ten on its half equator. Medullary shells both compressed, lenticular. This species 

 resembles Cypassis entomocora vel Ommatocampe trinacria, Stohr, 1880, loc. cit., p. 90, Taf. ii. fig. 1, 

 but has not its external mantle. It may be the ancestral form of it (both in an ontogenetic and 

 phylogenetic sense). 



Dimensions. Main axis Oil, equatorial axis 0'07 ; greatest breadth O'OS ; pores O'OOS, 

 liars 0-005. 



Habitat. Fossil in Tertiary rocks of Sicily, Caltanisetta, Haeckel (Grotte, Stohr ?). 



5. Cyphonium diattus, n. sp. 



Cortical shell thin walled, with quite smooth surface ; pores irregular, polygonal, mostly 

 pentagonal or hexagonal, three to six times as broad as the bars ; six to seven on the half 

 meridian of each chamber, ten to twelve on its half equator. Medullary shells both spherical. 

 (Resembles Cyphonium profundum, Ehrenberg, 1872, loc. cit, Taf. x. fig. 5, but does not possess 

 the spines of the surface.) 



Dimensions. Main axis 013, equatorial axis 0'06 ; greatest breadth 0'08 ; pores 0'005 to - 012, 

 bars 0-002 to 0'004. 



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



6. Cyphonium mammarium, n. sp. 



Cortical shell thick walled, with smooth surface (sometimes a little rough) ; pores irregular, 

 roundish, twice to three times as broad as the bars ; eleven to twelve on the half meridian of each 

 chamber, sixteen to nineteen on its half equator. Internal medullary shell spherical, external 

 lenticular compressed, sometimes both spherical or both compressed. (Resembles the internal 

 cortical twin-shell of CypJwcolpus virginis, PL 40, fig. 11.) 



Dimensions. Main axis 014, equatorial axis 0'08, greatest breadth 0'09 ; pores 0'004 to O'OOG, 

 bars 0-002. 



Habitat. South Pacific, Station 285, depth 2375 fathoms. 



Subgenus 2. Ommatocyrtis, Haeckel. 

 Definition. Surface of the cortical shell thorny or spiny. 



7. Cyphonium hexagonium, n. sp. 



Dulymocyrtis hexagonia, Haeckel, 1881, Prodromus. 



Cortical shell thin walled, with spiny surface ; pores regular or subregular, hexagonal, twice to 

 i liree times as broad as the bars ; five to six on the half meridian, nine to ten on the half equator 



