Much has been written about ammonites, commonly known as snakestones, in English folklore. The fascination with snakestones centred particularly around two places in England - Whitby in Yorkshire, and Keynsham in Somerset - where ammonites are common.
Snakestones were alluded to as early as the sixteenth century. William Camden in the book Britannia (1586) stated that, 'if you break them you find within stony serpents, wreathed up in circles, but eternally without heads'.
Legend has it that the ammonites are the petrified remains of snakes that once infested the Whitby area. The infestation was brought to an end by the Saxon Abbess St Hilda (614-680 AD) who turned the snakes into stone in order to clear a site for the building of an abbey.
St Hilda's actions are immortalised in Sir Walter Scott's poem Marmion :
When Whitby's nuns exalting told,
Of thousand snakes, each one
Was changed into a coil of stone,
When Holy Hilda pray'd:
Themselves, without their holy ground,
Their stony folds had often found.
The fact that Whitby snakestones generally do not have a head is supposedly due to a convenient beheading curse issued by another Christian martyr, St Cuthbert.
However, to make snakestones more saleable, and to reinforce the legend of their origin, serpents' heads were sometimes carved onto them (Mackie 1858), especially in victorian times.