Page:Scientific results HMS Challenger vol 18 part 1.djvu/746

538 Dimensions.—Radius of the odd arm 0.2, of the paired arms 0.15; distal breadth of the former 0.08, basal breadth 0.04; breadth of the paired arms 0.04.

Habitat.—South Atlantic, Station 325, surface.

4. Chitonastrum dicranoides, n. sp.

All three arms in the basal half simple, nearly square, in the distal half forked; branches straight, blunt. Odd arm twice as large as the paired arms; angle between the latter larger than the angles between them and the odd arm. (The form of the arms resembles Dicranastrum furcatum, Pl. 47, fig 2.)

Dimensions.—Radius of the odd arm 0.24, of the paired arms 0.12; basal breadth 0.06.

Habitat.—North Atlantic, Station 353, surface.

5. Chitonastrum lyra, n. sp. (Pl. 43, fig. 15).

Dictyastrum lyra, Haeckel, 1881, Prodromus et Atlas (pl. xliii. fig. 15).

All three arms forked and nearly of the same size, but different in form and position. The distance between the branches of the two paired arms is only one-fourth of the distance between them and the odd arm. Each arm in the basal two-thirds is simple, with eleven to twelve transverse septa, in the distal third forked, each branch with four to five transverse septa. The branches of each arm are curved convexly one to another, ending obtusely. The axis of the simple proximal part is straight in the odd arm, in the paired arms curved concavely towards the middle line. In the figured specimen, which I observed living in Portofino (in September 1880), the central chamber of the central disk and the first surrounding ring were filled with the nucleus of the cell; both external rings were filled (like all chambers of the arms) with pink oil-globules of the red central capsule. From the mantle, enveloping the shell, radiated innumerable fine pseudopodia (much too short in the figure), and between the two paired arms a long "sarcode-flagellum."

Dimensions.—Radius of each arm 0.16; greatest breadth of the odd arm 0.04; basal breadth of the paired arms 0.02; distance of both branches of each arm 0.08.

Habitat.—Mediterranean, Portofino, near Genoa, Haeckel.

Definition.— with three forked, chambered arms, connected by a patagium. (Arms and angles between them either equal or unequal.)

The genus Trigonastrum differs from the preceding Chitonastrum, its ancestral form, in the development of a patagium between the arms. It bears therefore to the latter the same relation that Euchitonia does to Rhopalastrum.