Numerous preparations of Aulacanthida exhibited a central capsule with two nuclei (Pl. [101], fig. 6), or a calymma with two central capsules (Pl. [104], figs. 1, 3); so that the process of propagation by self-division, observed already in many different Phæodaria, seems to happen very frequently in the Aulacanthida. The voluminous phæodium is usually about twice or three times as large as the central capsule, and covers its oral or anterior half; the colour of the roundish phæodella composing it is sometimes more green or brown, at other times more blackish. The roundish alveoles, which fill up the rather firm jelly of the calymma, exhibit nearly the same shape as in the common Thalassicolla nucleata. The surface of the calymma is usually protected by the dense veil of tangential needles, and often forms conical or tent-shaped elevations around the bases of the piercing radial tubes (Pl. [102], fig. 1).
Synopsis of the Genera of Aulacanthida.
| Radial tubes simple, without lateral and terminal branches. |  | Surface of the calymma naked, without tangential needles, | 665. Aulactinium. |
| Surface of the calymma covered by a veil of tangential needles, | 666. Aulacantha. | ||
| Radial tubes without lateral branches, but with a verticil of terminal branches. |  | Terminal branches simple, | 667. Aulographis. |
| Terminal branches forked or again ramified, | 668. Auloceros. | ||
| Radial tubes with lateral and with terminal branches. | | Lateral branches verticillate, | 669. Aulospathis. |
| Lateral branches irregularly scattered, not verticillate, | 670. Aulodendron. |
| Radial tubes simple, without lateral and terminal branches. | ||||
| Surface of the calymma naked, without tangential needles, | ||||
| 665. Aulactinium. | ||||
| Surface of the calymma covered by a veil of tangential needles, | ||||
| 666. Aulacantha. | ||||
| Radial tubes without lateral branches, but with a verticil of terminal branches. | ||||
| Terminal branches simple, | ||||
| 667. Aulographis. | ||||
| Terminal branches forked or again ramified, | ||||
| 668. Auloceros. | ||||
| Radial tubes with lateral and with terminal branches. | ||||
| Lateral branches verticillate, | ||||
| 669. Aulospathis. | ||||
| Lateral branches irregularly scattered, not verticillate, | ||||
| 670. Aulodendron. | ||||
Subfamily 1. Aulactinida, Haeckel.
Definition.—Aulacanthida without external veil of tangential needles on the surface of the calymma.
Genus 665. Aulactinium,[[283]] n. gen.
Definition.—Aulacanthida without a veil of tangential needles, with simple radial tubes, which bear neither lateral nor terminal branches.
The genus Aulactinium differs from all the other Aulacanthida in the complete absence of the characteristic fine tangential needles, which constitute in the latter an arachnoidal veil or mantle around the spherical calymma. We accordingly divide the whole family into two subfamilies, the Aulactinida with a naked calymma, and the Aulographida with a veil of tangential needles. The radial tubes possess in the few species of Aulactinium observed a very simple shape, as in the closely allied Aulacantha.
1. Aulactinium actinastrum, n. sp. (Pl. [101], figs. 6, 7).