Sea-urchin Small 318×320 Medium 635×640 Large 1017×1024 Download Tiff Original 2383×2400 | (5.5 MB) Description Sea-urchins are Echinoderms. Their shell is mainly composed of calcareous plates. Keywords Echinoderm, Echinodermata, sea-urchin, test Galleries Sea Urchins and Sea Stars Source: H. Alleyne Nicholson, An Introductory Text-book of Zoology(Edinburgh:William Blackwood and Sons, 1971) 50
