Defn: 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.
AMMONITIFEROUS
Am`mon*i*tif"er*ous, a. Etym: [Ammonite + -ferous.]
Defn: Containing fossil ammonites.
AMMONITOIDEA
Am*mon`i*toid"e*a, n. pl. Etym: [NL., fr. Ammonite + -oid.] (Zoöl.)
Defn: An extensive group of fossil cephalopods often very abundant in
Mesozoic rocks. See Ammonite.
AMMONIUM
Am*mo"ni*um, n. Etym: [See Ammonia.] (Chem.)
Defn: A compound radical, NH4, having the chemical relations of a strongly basic element like the alkali metals.
AMMUNITION Am`mu*ni"tion, n. Etym: [F. amunition, for munition, prob. caused by taking la munition as l'amunition. See Munition.]
1. Military stores, or provisions of all kinds for attack or defense. [Obs.]
2. Articles used in charging firearms and ordnance of all kinds; as powder, balls, shot, shells, percussion caps, rockets, etc.