Echinidea–Igelsterne from Kunstformen der Natur (1904) by Ernst Haeckel. Original from Library of Congress. Digitally… https://www.rawpixel.com/image/2272987/free-illustration-image-ernst-haeckel-sand-dollar-vintageFree Image from public domain license
Great Barrier Reef Echinoderms from The Great Barrier Reef of Australia (1893) by William Saville-Kent (1845-1908). https://www.rawpixel.com/image/414424/free-illustration-image-coral-fish-reefFree Image from public domain license
Different types of sea urcnhins illustrated by Charles Dessalines D' Orbigny (1806-1876). Digitally enhanced from our own… https://www.rawpixel.com/image/324914/free-illustration-image-sand-dollar-sea-urchinFree Image from public domain license