Dimensions.—Diameter of the disk 0.15 to 0.25; length of the radial spines 0.03 to 0.06, basal breadth 0.004 to 0.01.
Habitat.—Pacific, central area, Stations 270 to 274, in 2350 to 2925 fathoms.
Genus 259. Spongotrochus,[[298]] Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 844.
Definition.—Spongodiscida with numerous solid radial spines (five to ten or more), which are scattered over the whole surface and the margin of the disk, or regularly disposed on both sides of it.
The genus Spongotrochus differs from the foregoing and nearly allied genus by the distribution of the numerous radial spines. These are not confined to the margin of the disk, but also scattered on its whole surface, and sometimes symmetrically disposed on both its sides in a regular manner. Also in this genus the spongy framework is sometimes quite irregular (Spongotrochiscus), at other times in the middle part with enclosed concentric rings (Stylospongidium).
Subgenus 1. Spongotrochiscus, Haeckel, 1862, Monogr. d. Radiol., p. 463.
Definition.—Spongy framework of the whole disk irregular, without concentric rings or spiral convolutions.
1. Spongotrochus brevispinus, Haeckel.
Spongotrochus brevispinus, Haeckel, 1862, Monogr. d. Radiol., p. 462, Taf. xxvii. figs. 4, 5.
Spongy framework of the whole disk irregular, everywhere equal. The whole surface of the disk covered with numerous short, needle-shaped, radial spines, about as long as the thickness of the disk, which is one-fifth of its diameter.