Types of the Ovum Anguinum. Echinites (sea-urchins). From Aldrovandi’s “Museum metallicum,” Bononiæ, 1648. ] The serpent-stone, called by Pliny _ovum anguinum_, or “serpent’s egg,” is said to have been worn by the Druid priests as a badge of distinction. Pliny relates that he had seen one of them which was as large as a moderate-sized apple, its shell being a cartilaginous substance. It was supposed to be generated in midsummer out of the saliva and slime exuding from a knot of intertwined serpents. When the moisture had coagulated and formed into a sphere, this was tossed in the air by the hissing snakes, and, in order to preserve its efficacy as a talisman, the finder had to catch it in a linen cloth before it fell to the ground. Such “serpent’s eggs” were in high favor with the Romans, who believed they procured for the wearers success in all disputes and the protection of kings. So great was the faith reposed in their magical virtues that Claudius is said to have condemned to death a Roman knight, one of the Vecontii, simply because he had an _ovum anguinum_ concealed in his bosom when he appeared in court during the trial of a lawsuit in which he was involved. In order to enhance the value of this amulet, the story was circulated that great dangers were incurred in securing it; for the snakes pursued any one who seized the egg and he could only escape by fording a river, across which they could not swim.[446] In later accounts of this amulet it is described as a ring, sometimes composed of a blue stone with an undulating streak or stripe of yellow, thought to represent a snake. Certain so-called floating-stones have been found in a branch of Mann Creek, a tributary of the Weiser River, which flows into the latter near its confluence with the Snake River in Idaho.[447] These are hollow quartz globes, with a shell so thin that the air in the cavity more than makes up for the specific gravity of the quartz. Some formation similar to this may possibly have been intended by Pliny in his description of the _ovum anguinum_ or serpent’s egg of the Druids, which floated if thrown into a stream, although it is perhaps more probable that these “serpent’s eggs” were shells of the sea-urchin, as they are figured by De Boot and other writers.