CORNU Ammonis, in natural history, fossil shells,
called also serpent-stones, or snake-stones.
They are found of all sizes, from the breadth of a
sixpence, to more than two feet in diameter; some
of them rounded, others greatly compressed, and
lodged in different strata of stones and clays; some a-
gain are smooth, and others ridged in different man-
ners, their striae and ridges being either straight, ir-
regularly crooked, or undulated. See SNAKE-STONE.