aptychus
Ap"ty*chus, n. Etym: [NL., fr. Gr. (Zoöl.) Defn: A shelly plate found in the terminal chambers of ammonite shells. Some authors consider them to be jaws; others, opercula.
Ap"ty*chus, n. Etym: [NL., fr. Gr. (Zoöl.) Defn: A shelly plate found in the terminal chambers of ammonite shells. Some authors consider them to be jaws; others, opercula.