Page:Scientific results HMS Challenger vol 18 part 1.djvu/330

122

Definition.— with one simple spherical lattice-shell.

Definition.— with one single lattice-sphere and two free spines of equal size and form.

The genus Xiphosphæra is the most simple form of all Stylosphærida, and may be regarded as the common ancestral form of this family. On the surface of a simple