The genus Auloscena differs from the preceding Aulosphæra, its ancestral form, in a very remarkable and elegant character. The tangential tubes of the network here lie not on a spherical face (as in the latter), but arise over the surface of the spherical calymma in the form of numerous, regular, hexagonal pyramids; each pyramid being composed of six convergent ascending tubes, which are united in a common nodal point; at the latter arises a radial tube, which usually bears an elegant corona of radially divergent terminal branches. Therefore the base of each hexagonal pyramid is in contact at its six corners with the basal corners of six similar neighbouring pyramids, whilst the neighbouring sides of the bases are separated by six regular triangular meshes, which lie on the spherical face. In some species this remarkable and elegant structure is quite regular, whilst in others it becomes more or less irregular.
Subgenus 1. Auloscenium, Haeckel.
Definition.—Radial tubes smooth, without lateral branches or spines, bearing a terminal verticil at the distal end.
1. Auloscena mirabilis, n. sp. (Pl. [110], figs. 1, 2).
Radial tubes cylindrical, straight, smooth, about as long as the smooth pyramidal tubes (or the convergent tubes which form the edges of the six-sided pyramids of the network). The distal end of each radial tube bears an elegant spathillate terminal corona (fig. 2), or a verticil of fifteen to twenty curved radial branches, the distal end of which is armed with a spinulate knob.
Dimensions.—Diameter of the sphere 2.0 to 3.0; pyramidal tubes 0.16 to 0.24 long, 0.008 broad.
Habitat.—Central Pacific, Stations 271 to 274, depth 2350 to 2750 fathoms.
2. Auloscena spectabilis, n. sp. (Pl. [110], figs. 8, 9).
Radial tubes cylindro-conical, straight, smooth, twice as long as the smooth pyramidal tubes, armed at the distal end with a conical terminal corona, or a verticil of twelve to sixteen divergent, straight, pointed, terminal branches.
Dimensions.—Diameter of the sphere 4.0 to 5.0; pyramidal tubes 0.25 to 0.3 long, 0.012 broad.