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



2. Cromyechinus dodecacanthus, n. sp. (PI. 30, figs. 3, 3a). 



Eadial proportion of the four spheres = 1 : 3 : 10 : 12. Outer cortical shell very delicate, with 

 very small, regular, circular pores, covered with numerous short bristle-shaped by-spines, scarcely 

 one-fourth as long as the radius ; inner cortical shell with very large, irregular, polygonal pores, 

 twice to six times as broad as the bars. Both medullary shells with very small, regular, circular 

 pores, connected with the former by twelve regularly disposed, thin radial beams ; these are pro- 

 longed outside into twelve strong, three-sided pyramidal main spines, one-third as long as the shell 

 diameter. (Differs from the foregoing only in the number and form of the radial spines.) 



Dimensions. Diameter of the four sheUs (A) 012, (B) 01, (C) 0'03, (D) O'Ol ; pores of the 

 outer cortical shell 0'002, of the inner 0'02, bars 0'002 ; length of the spines 0'04, basal breadth 



o-oi. 



Habitat. South Atlantic, Station 325, surface. 



3. Cromyechinus polyacanthus, n. sp. 



Eadial proportion of the four spheres = 1 : 2 : 8 : 10. Outer cortical shell of the same structure 

 as the inner, with irregular, roundish pores, twice to six times as broad as the bars. Both medullary 

 shells with small, regular, circular pores, twice as broad as the bars. Connecting radial beams forty 

 to sixty, thin, cylindrical, prolonged outside into forty to sixty strong conical main spines, about as long 

 as the radius. Between these, numerous thin bristle-shaped by-spines, nearly of the same length. 



Dimensions. Diameter of the four shells (A) 0'25, (B) 0'2, (C) 0'05, (D) 0'025 ; pores of both 

 cortical shells O'Ol to 0'03 ; length of the spines 012. 



Habitat. North Pacific, Station 237, surface. 



Genus 106. Cromyodrymus, 1 Haeckel, 1881, Prodromus, p. 454. 



Definition. A strosphaerida with four concentric lattice-spheres and numerous 

 branched radial spines. 



The genus Cromyodrymus differs from its ancestral form, Cromyomma, in the 

 ramification of the radial spines, and exhibits therefore the same relation to it that 

 Pityomma among the Actinommida bears to Actinomma. 



1. Cromyodrymus quadricuspis, n. sp. (PI. 30, figs. 7, 7 a). 



Radial proportion of the four shells = 1 : 3 : 6 : 12. All four shells with regular, circular pores, 

 about twice as broad as the bars. Eadial proportion of the pores in the four shells = 2:4:2:1. 

 Eadial spines fifty to sixty, three-sided prismatic, half as long as the radius, with three recurved 

 teeth, each spine in this way bearing four points. 



1 Cromyodrymus = Onion with trees ; 



