See Horn.

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, and some even larger; some of them rounded, others greatly compressed, and lodged in different strata of stones and clays; some again are smooth, and others variously ridged, their thine and ridges being either straight, irregularly crooked, or undulated. See Snake Stones.

Corno Cerii. See HARTSHORN.