6. There is a difference between a ‘portent’ (portentum) and ‘an unnatural being’ (portentuosus). Portents are beings of transformed appearance, as, for instance, is said to have happened when in Umbria a woman gave birth to a serpent. Whence Lucan says (Civil War 1.563): And the child terrified its own mother. But an unnatural being strictly speaking takes the form of a slight mutation, as for instance in the case of someone born with six fingers.