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



7. Actinomma denticulatum, n. sp. (PI. 29, fig. 3). 



Cortical shell thick walled, with regular, circular, double-edged pores, twice as broad as the 

 bars. Forty to fifty radial spines, three-sided pyramidal, half as long as the radius, with three 

 elegantly denticulated edges. Kadial proportion of the three spheres = 1:2:5. (Differs from 

 Haliomma denticulatum only in the double medullary shell and larger size.) 



Dimensions. Diameter of the outer shell 014, middle 0'06, inner 0'03 ; cortical pores OD1, 

 bars 0'005 ; length of the spines 0'04, basal breadth 001. 



Habitat. Central Pacific, Station 271, depth 2425 fathoms. 



8. Actinomma trinacrium, Haeckel. 



Actinomma trinacrium, Haeckel, 1862, Monogr. d. Radiol., p. 441, Taf. xxiv. figs. 6-8. 

 Haliomma trinacrium, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 815. 



Cortical shell as well as both medullary shells thin walled, with subregular, circular pores, 

 twice as broad as the bars. Badial proportion of the three spheres = 1:3:9; radial beams 

 between them twenty, prolonged outside into strong, three-sided pyramidal spines, as long as 

 the radius ; between them, on the surface, numerous similar spines. Sometimes the latter remain 

 smaller, the pores more irregular, and then this species corresponds to Ecliinomma trinacrium. 



Dimensions. Diameter of the outer shell 0'09, middle 0'03, inner O'Ol ; cortical pores 0'008, 

 bars 0-004 ; length of the spines 0'04, basal breadth O'Ol. 



Habitat. Mediterranean (Messina, Corfu, Haeckel), surface. 



9. Actinomma pachyderma, n. sp. (PL 29, figs. 4, 5). 



Cortical shell very thick walled, with regular, circular, double-edged pores, twice as broad as 

 the bars. Both medullary shells with simple, small, circular pores, of the same breadth as the 

 bars. Eadial proportion of the three spheres = 1:2:4; radial spines about twenty, conical, 

 shorter than the radius, prolonged inside into twenty very thin connecting beams (fig. 4). 



Dimensions. Diameter of the outer shell 0'08, middle 0'04, inner 0'02 ; cortical pores O'Ol 

 bars 0-005 ; length of the spines 0'03, basal breadth O'Ol. 



Habitat. South Pacific, Station 297, depth 1775 fathoms. 



Subgenus 3. Actinommilla, Haeckel. 



Definition. Pores of the cortical shell irregular, of different size and form ; spines 

 over the entire surface (commonly one spine at each nodal-point). 



10. Actinomma spinigerum, Stolir. 



Actinomma spinigerum, Stohr, 1880, Palseontogr., vol. xxvi. p. 92, Taf. ii. tig. 10. 



Cortical shell thick walled, with irregular, roundish, or subcircular pores, twice to four times as 

 broad as the bars. Eadial proportion of the three spheres =1:3:8; between them eight (?) con- 



