a. (sb.) [f. as prec.: see RADIATE a. and -ATE2 2.] Having or consisting of three rays; radiating in three directions from a central point; three-rayed, trifurcate.
1846. Patterson, Zool., 60. Three beautiful little semicircular horny saws, arranged in a triradiate manner, so that their edges meet in the centre.
1874. Cooke, Fungi, 36. The triradiate spores of Asterosporium.
1875. Huxley, in Encycl. Brit., I. 754/2. Each pterygoid … is a triradiate bone, with an anterior, an inner, and a posterior, or outer, ray.
B. sb. A triradiate sponge-spicule.
1887. Sollas, in Encycl. Brit., XXII. 417/1. (Sponges) The shorter paired rays being termed basal, and the whole spicule a sagittal triradiate.
1911. A. Dendy, in Encycl. Brit., XXV. 722/1. The triradiates and quadriradiates … are not simple spicules, but spicule-systems formed of three or four rays each originating independently from its own scleroblast.
So Triradiated a. = triradiate; Triradiately adv., in a triradiate manner (Cent. Dict., 1891); Triradiation, radiation in three directions; also, a triradiate figure or structure.
1786. Phil. Trans., LXXVI. 160. The cavity … is divided into … chambers or compartments by solid transverse septa, which communicate with each other by a triradiated aperture.
c. 1900. Buck’s Handbk. Med. Sc., II. 177. The callosal eminence…, the hippocamp, and the occipital eminence form an irregular triradiation.
