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



3. Pleuraspis costata, Haeckel. 



Acanthometra costata, J. Miiller, 1858, Abhandl. d. k. Akad. d. Wisa. Berlin, p. 49, Taf. ii. 



fig. 1, Taf. x. figs. 4-6. 

 Dorataspis costata, Haeckel, 1862, Monogr. d. Radiol., p. 414, Taf. xxiii. fig. 1. 



Radial spines roundish, conical, pointed at both ends ; outer and inner halves of nearly equal 

 length. Two apophyses of each spine simply forked, with broad branches and thickened condyles. 

 Forty sutures, broad. Twenty-two large meshes, four to five tunes as broad as the bars. By-spines 

 straight, denticulate, half as long as the radius. (This common species is rather variable in size 



and details.) 



Dimensions. Diameter of the shell 01 to 013, meshes 0'03 to 0'06, bars 0'005 to O'Ol. 

 Habitat. Cosmopolitan ; Mediterranean, Atlantic, Pacific, surface. 



4. Pleuraspis pyramidalis, n. sp. 



Eadial spines quadrangular, their outer part pyramidal, very thick, about half as long as the 

 prismatic inner part. Two apophyses of each spine simply forked, with very short and broad 

 branches. Condyles much thickened. Forty sutures, very broad. Twenty-two meshes small, 

 the largest twice as broad as the bars ; the smaller only half as broad. By-spines short, straight, 

 denticulate, half as long as the radius. 



Dimensions. Diameter of the shell 014, meshes 0'005 to 0'03. 



Habitat. Western Tropical Pacific, Station 222, surface. 



Subgenus 2. Pleuraspidium, Haeckel. 



Definition. Shell with forty to eighty or more meshes and eighty to one 

 hundred or more sutures; each spine with six to eight or more branches, its two 

 apophyses being forked twice or oftener. 



5. Pleuraspis ramosa, n. sp. 



Eadial spines roundish, stout, somewhat compressed; their inner and outer half nearly of 

 equal length. Two apophyses of each spine doubly forked or more irregularly branched ; there- 

 fore commonly eight (sometimes six, seven, nine, or ten to twelve) thickened condyles on each 

 spine. Sutures eighty to one hundred, broad. Irregular meshes sixty to eighty ; three to five 

 times as broad as the bars. By-spines zigzag, ramified, half as long as the radius. 



Dimensions. Diameter of the shell 015, of the meshes O'OOV to 0-014, breadth of the 

 bars 0-003. 



Habitat. Central Pacific, Station 272, surface. 



