Genus 322. Acanthochiasma,[[362]] Krohn, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 810.
Definition.—Chiastolida with ten diametral spines, derived from twenty radial spines opposite and grown together in pairs.
The genus Acanthochiasma with a small number of common species, comprises the Chiastolida with ten diametral spines, which are loosely crossed in the centre of the body. I could distinguish only four species, two of which are cosmopolitan and very widely distributed. In all four species the diametral spines are quite simple, cylindrical; only in one species distinguished by a spiral winding or torsion in the middle part, where they are crossed one to another. We derive Acanthochiasma from Acanthometron by concrescence of every two spines opposite in one axis of the body.
1. Acanthochiasma krohnii, Haeckel.
Acanthochiasma krohnii, Haeckel, 1862, Monogr. d. Radiol., p.403, Taf. xix. fig. 7.
Acanthochiasma krohnii, R. Hertwig, 1879, Organismus d. Radiol., Taf. ii. fig. 6.
Spines needle-shaped, cylindrical, very thin and long, of equal breadth in their whole length, distinguished by a high degree of elasticity. Central capsule colourless or yellowish-white, transparent. Granules of the sarcode colourless.
Dimensions.—Length of the spines 0.5 to 1.0, breadth 0.001 to 0.002.
Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, very common.
2. Acanthochiasma rubescens, Krohn.