3. Pleuraspis costata, Haeckel.
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 times 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 0.1 to 0.13, meshes 0.03 to 0.06, bars 0.005 to 0.01.
Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.
4. Pleuraspis pyramidalis, n. sp.
Radial 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 0.14, 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.
Radial 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; therefore 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 0.15, of the meshes 0.007 to 0.014, breadth of the bars 0.003.
Habitat.—Central Pacific, Station 272, surface.
