Dimensions.—Length of the spines 0.15 to 0.18, of the middle rod 0.015.
Habitat.—South Pacific, Station 288, surface.
Subfamily 4. Polyplagida, Haeckel, 1881, Prodromus, p. 424.
Definition.—Plagonida with numerous (seven to nine or more) radial spines.
Genus 392. Polyplagia,[[11]] n. gen.
Definition.—Plagonida with numerous (seven to nine or more) radial spines, arising from a common centre and lying in different planes.
The genus Polyplagia alone represents the small subfamily of Polyplagida, distinguished from the other Plagonida by the multiplication of the radial spines, the number of which amounts to seven to nine or more. This increased number is commonly the result of an intercalation of new spines between the three or four primary spines; it is sometimes also effected by stronger development of branches of the latter, which become independent. The following five species of this genus are very different, require further investigation, and perhaps represent different genera:—
1. Polyplagia septenaria, n. sp.
Seven radial spines, straight, three-sided prismatic, verticillate, of different sizes; four larger spines correspond to the four axes of a tetrahedron (running from the centre to the four corners), each with five to six verticils of three simple slender branches; one of these four main spines seems to be the apical, the three others the basal spines of Plagiocarpa; in the three meridian planes between the latter and the former lie the three smaller spines, diverging upwards, each with two to three verticils. (Similar to Polyplecta heptacantha, Pl. [91], fig. 12, but without connection between the branches.)
Dimensions.—Length of the four major spines 0.26, of the three minor 0.11.