Dimensions.—Diameter of the innermost shell 0.1; distance between the concentric shells 0.05.
Habitat.—Central Pacific, Station 271, surface.
2. Arachnopila polygonella, n. sp.
Innermost shell with irregular, polygonal pores; its diameter fully as long as the equal distance between every two concentric shells. Radial spines sixty to eighty, each with twelve to sixteen verticils.
Dimensions.—Diameter of the innermost shell 0.04; distance between the concentric shells 0.04.
Habitat.—Central Pacific, Station 266, surface.
Genus 109. Arachnopegma,[[147]] Haeckel, 1881, Prodromus, p. 454.
Definition.—Astrosphærida with five to ten or more cortical, concentric, polyhedral, or spherical lattice-shells, composed of a very thin, cobweb-like network; innermost shell with hexagonal or polygonal meshes; other shells with simple triangular meshes, connected to one another by diagonal threads between them.
The genus Arachnopegma differs from its ancestral form Arachnopila, in the possession of peculiar diagonal threads, which connect the verticils or nodal-points of every two neighbouring radial spines in two different neighbouring concentric shells. In this case, therefore, not only do triangular meshes lie in the spherical faces of the concentric spheres, but also between them, in numerous oblique diagonal planes; a very rare and remarkable structure, and forming a transition to spongy shells.
1. Arachnopegma verticillatum, n. sp.