50. & 51. Atlantic horseshoe crab (Polyphemus occidentalis) illustration from Zoology of New York (1842–1844) by James… https://www.rawpixel.com/image/329365/free-illustration-image-crab-horseshoe-zoology-new-yorkFree Image from public domain licenseAspidonia–Schildtiere from Kunstformen der Natur (1904) by Ernst Haeckel. Original from Library of Congress. Digitally… https://www.rawpixel.com/image/2272991/free-illustration-image-ernst-haeckel-biology-jellyfishFree Image from public domain licenseHorseshoe crab: dorsal and ventral views. Watercolour by Zayhn al-Din, 1777/1783. https://www.rawpixel.com/image/13969833/image-cartoon-art-watercolourFree Image from public domain license