Aptychus

1 definition found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Aptychus \Ap"ty*chus\, n. [NL., fr. Gr. 'a priv. + ?, ?, fold.]
     (Zool.)
     A shelly plate found in the terminal chambers of ammonite
     shells. Some authors consider them to be jaws; others,
     opercula.
     [1913 Webster]