a. and sb. Zool. [f. TETRA- + Gr. ἀκτ-ίς ἀκτῖν- ray.] a. adj. Having four rays or branches; quadriradiate. b. sb. A four-rayed sponge-spicule. So Tetractinal a., Tetractine a. and sb., Tetractinose a.
1886. Proc. Zool. Soc., 21 Dec., 581. The chief spicules are tetract.
1887. Sollas, in Encycl. Brit., XXII. 416. (Fig. 12) d. calthrops (tetraxon tetractine). Ibid. (1888), in Challenger Rep., XXV. p. lix. Tetractine.—When all four actines of a tetraxon are present it is … a tetractine, but as the full designation of this required to distinguish it from a tetractinose triaxon is tetractine tetraxon, we shall substitute for it the equivalent ‘calthrops.’
1891. Cent. Dict., Tetractinal.
