Tetract(in(e))

Definition

In C., D.; H.; in D. any spicule with four rays ordered in different planes (e.g., calthrop, triaene); in C. any spicule with four rays; most of them have three actines in the same plane and the fourth one (apical) is perpendicular to them, however all the four actines can be in the same plane, the fourth being opposite to the unpaired actine (see pugiole); T. may be fused by their basal actines creating a fused skeleton (e.g., genus Plectroninia); in H. any spicule with four rays.

Synonyms

Quadriradiate

Photos