Page:Scientific results HMS Challenger vol 18 part 1.djvu/245

Rh The genus Lampoxanthium differs from the foregoing, Thalassoplancta, by the composite form of the spicula, which are not simple needles, but radiate or geminate, or branched in different forms; the former stands therefore in the same relation to the latter as the social Belonozoum to Sphærozoum. The spicula of some species of Lampoxanthium are identical with those of some species of Sphærozoum, so that the latter may be derived from the former by forming colonies. The large central capsule is enveloped by a very voluminous alveolated calymma, and includes a large central nucleus with numerous nucleoli.

Definition.—Spicula all (or nearly all) of one kind, radiate.

1. Lampoxanthium tetractinium, n. sp.

Spicula all (or nearly all) tetraradiate, with four thorny, straight, pointed shanks, radiating from one common point. (Intermingled with these are often some few, thorny, triradiate spicula.) On the inside of the capsule a layer of large oil-globules as in Thalassoplancta, Pl. 2, fig. 2.

Dimensions.—Diameter of the central capsule 0.2, of the nucleus 0.08, of the calymma 0.8.

Habitat.—South Pacific, Station 288, surface.

Definition.—Spicula all (or nearly all) of one kind, geminate-radiate, with a simple middle rod and two to four diverging shanks on each end of it.

2. Lampoxanthium punctatum, n. sp.

Spicula all geminate-triradiate, thorny, of the same form as in the common Sphærozoum punctatum, of which this species is the large solitary representative. The spicula are aggregated in a very condensed layer on the surface of the large calymma.

Dimensions.—Diameter of the capsule 0.8, of the nucleus 0.6, of the calymma 2.0.

Habitat.—North Pacific, Station 248, surface.

3. Lampoxanthium octoceras, n. sp.

Spicula all geminate-quadriradiate, with a very short simple middle rod and four very long divergent shanks on both ends of it; the shanks are smooth, five to ten times as long as the middle