acrania

1 definition found

acrania - Collaborative International Dictionary of English v.0.48 :

  Acrania \A*cra"ni*a\, n. [NL., from Gr. 'a priv. + ? skull.]
     1. (Physiol.) Partial or total absence of the skull.
        [1913 Webster]
  
     2. pl. (Zool.) The lowest group of Vertebrata, including the
        amphioxus, in which no skull exists.
        [1913 Webster]