Heptaplegma heptacantha, Haeckel, 1882, MS.
Seven unequal spines divergent from one common central point, slender, slightly curved, three-sided prismatic. Four spines are much larger, twice to three times as long and as thick as the three smaller spines. One of the four larger spines is directed upwards (as "apical horn"), whilst the three others diverge downwards (as "basal feet"). Each of the four larger spines bears five to seven equidistant verticils of three divergent branches, the proximal of which are branched, the distal simple. The three smaller spines lie nearly horizontally, midway between the odd apical spine and the three basal spines, and in the same meridian planes with them; each bears one verticil of three divergent branches. All the branches are united by arachnoidal threads, composing a loose wickerwork with irregular, generally quadrangular meshes.
Dimensions.—Length of the four larger spines 0.27 to 0.33, of the four smaller 0.1 to 0.14.
Habitat.—Central Pacific, Station 271, surface.
2. Polyplecta enneacantha, n. sp.
Enneaplegma enneacantha, Haeckel, 1881, Prodromus, p. 425.
Nine equal and equidistant, straight, cylindrical radial spines, lying nearly in one plane, arise from an irregular spongy central framework; six of them seem to be secondary, intercalated between three equidistant primary spines, which are united in the centre. (This species resembles in the nine-radial structure the remarkable Enneaphormis rotula, Pl. [57], fig. 9, and may perhaps be derived from a similar species; but it has no regular latticed shell.)
Dimensions.—Length of the spines 0.22, diameter of the framework 0.17.
Habitat.—Central Pacific, Station 266, depth 2750 fathoms.
3. Polyplecta decacantha, n. sp.