Hildoceras bifrons is an extinct species of ammonite in the family Hildoceratidae. It dates from about 175 million years ago in the Early Jurassic when it was both widespread and common. The genus name has been given the name Hildoceras in honour of St. Hilda of Whitby (614-680 AD). Legend has it that this lady was required to found an abbey on the cliffs above Whitby, in the north of England. Finding the site to be infested by snakes (a devilish omen), she prayed to the Lord and the snakes coiled up and were turned to stone. She picked them up and threw them over the cliff, and that is why there are so many ammonite fossils in the rocks below the abbey. The specific name bifrons comes from Bifron, a demon, another name for the Roman god, Janus.