The remaining Druid story in Pliny relates to a magic egg, the anguinum: reputedly made by the spittle and secretions of angry snakes, esteemed by the Druids and believed to ‘ensure success in law-courts and a favourable reception by princes’. Now Pliny had been shown an anguinum: ‘it was round and about as large as a smallish apple; the shell was cartilaginous and pocked very like the arms of a polypus’. A sea-urchin, denuded of its spines and fresh or fossil, has been suggested, but unconvincingly, since this would surely have been recognised for what it was by Pliny, and does not really accord with the description. A preferable alternative would be the ball of agglomerated empty egg-cases of a Whelk (Buccinum), which has a parchment-like texture and nodulated surface, for since Buccinum is a genus confined to Atlantic and northern waters, its egg-cases, common enough objects on a North Gaulish or British beach, might be quite unfamiliar to a Mediterranean naturalist, and so capable of being endowed for him with magic powers.
Thames & Hudson 1975