【医】 海马

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.

Ammonite \Am"mon*ite\, n. [L. cornu Ammonis born of Ammon; L.
Ammon, Gr. ? an appellation of Jupiter, as represented with
the horns of a ram. It was originally the name of an.
Egyptian god, Amun.] (Paleon.)
A fossil cephalopod shell related to the nautilus. There are
many genera and species, and all are extinct, the typical
forms having existed only in the Mesozoic age, when they were
exceedingly numerous. They differ from the nautili in having
the margins of the septa very much lobed or plaited, and the
siphuncle dorsal. Also called {serpent stone}, {snake stone},
and {cornu Ammonis}.