The Collaborative International Dictionary
Cornua Ammonis
Cornu Ammonis \Cor"nu Am*mo"nis\ ([a^]m*m[=o]"n[i^]s); pl. Cornua Ammonis. [L., horn of Ammon. See Ammonite.] (Paleon.) A fossil shell, curved like a ram's horn; an obsolete name for an ammonite.
Wiktionary
cornua ammonis
n. (plural of cornu ammonis English)