Dimensions.—Diameter of the whole jelly-sphere 8 to 12 mm., of the central capsule 5 to 10 mm., of the nucleus 1 to 2 mm., length of the spicula 0.1 to 0.3.
Habitat.—Eastern Atlantic, between Canary Islands and Cape Verde Islands, Meyen; Lanzerote, Haeckel.
Genus 10. Thalassoplancta,[[18]] Haeckel, 1862, Monogr. d. Radiol., p. 261.
Definition.—Thalassosphærida with numerous large alveoles in the calymma (but not in the central capsule), and with numerous simple, needle-shaped spicula around the central capsule.
The genus Thalassoplancta was founded by me in 1862 for a Radiolarian with simple hollow needles in the calymma, which was afterwards recognised as a Phæodarium, belonging to Cannorrhaphis. We here retain this name for a true Thalassosphærid, very similar to the latter, but distinguished by the absence of the phæodium and the solid—not hollow—needle-shaped spicula, which are scattered in the alveolated calymma. Thalassoplancta can be regarded as the solitary form of the social Belonozoum.[[19]]
1. Thalassoplancta longispicula, n. sp.
Spicula long and thin, cylindrical, smooth, more or less bent, pointed at both ends, similar to those of Thalassoplancta cavispicula. Central capsule thin-walled, without oil-globules, four times as broad as the nucleus, which encloses one single nucleolus.
Dimensions.—Diameter of the capsule 0.6, of the nucleus 0.15, of the calymma 4 mm.
Habitat.—North Atlantic, Færöe Channel (Gulf Stream), John Murray.
2. Thalassoplancta brevispicula, n. sp. (Pl. [2], fig. 2).