Page:Scientific results HMS Challenger vol 18 part 1.djvu/417

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Definition.— with one single spherical lattice-shell.

Wiss. Berlin, p. 12.

Definition.— with one simple lattice-sphere, covered with simple radial spines of the same kind.

The genus Acanthosphæra exhibits the most simple form of all Astrosphærida; a simple spherical lattice-shell, the surface of which is covered by radial spines of one and the same kind. The number of the latter is very variable, often twelve to twenty, regularly disposed; in other cases forty to sixty or more; and sometimes at each nodal-point of the network a spine is developed.