Caption:
Helicoprion with tooth whorl, genus of shark-like cartilaginous fish, and Xenacanthus, genus of prehistoric shark. Both became extinct in the Triassic. Colour printed (chromolithograph) illustration by F. John from "Tiere der Urwelt" Animals of the Prehistoric World, 1910, Hamburg. From a series of prehistoric creature cards published by the Reichardt Cocoa company.