Page:Scientific results HMS Challenger vol 18 part 1.djvu/239

Rh I described these two different species, the new Thalassosphæra bifurca and the Thalassosphæra morum, which J. Müller had formerly called Thalassicolla morum. This latter form is characterised by peculiar calcareous bodies "looking in outline like the rowels of spurs, scattered irregularly in the gelatinous envelope," and was therefore afterwards called "Calcaromma calcarea" by Sir Wyville Thomson. As already mentioned above, these calcareous rowels are foreign bodies, picked up by an Actissa (see p. 29). I here confine the genus Thalassosphæra to those solitary in which the body exhibits no alveoles, and the siliceous solid spicula in the calymma are quite simple needles.

Thalassosphæra belonium, n. sp.

Spicula thin cylindrical rods, more or less curved, pointed at both ends, with smooth surface (similar to the needles of Rhaphidozoum italicum). Central capsule spherical, three times as large as the central nucleus, without larger oil-globules.

Dimensions.—Diameter of the central capsule 0.1 to 0.12, length of the spicula 0.04 to 0.08.

Habitat.—Central Pacific, Station 272, surface.

Thalassosphæra rhaphidium, n. sp.

Spicula thick cylindrical rods, more or less curved, pointed at both ends, covered with numerous strong conical thorns, perpendicular to the axis. Central capsule spherical, four times as broad as the central nucleus, with twenty to thirty large oil-globules on the inside of the membrane.

Dimensions.—Diameter of the central capsule 0.2, length of the spicula 0.12 to 0.16.

Habitat.—Tropical Atlantic, Station 347, surface.

Definition.—Thalassosphærida without alveoles, with numerous branched or compound spicula in the calymma.

The genus Thalassoxanthium differs from the foregoing Thalassosphæra, by the ramification of the spicula, and has therefore the same relation to it as Sphærozoum to Belonozoum. The soft unicellular body is as simple as in Actissa, and exhibits alveoles neither in the capsule nor in the calymma.

Definition.—Spicula not geminate, but simply radiate, consisting of three, four, or more needles or shanks, radiating in different directions from one and the same point; shanks now simple or needle-like, now furcate or branched.