Hypertext Webster Gateway: "Acrania"
From Webster's Revised Unabridged Dictionary (1913) (web1913)
Acrania \A*cra"ni*a\, n. [NL., from Gr. 'a priv. + ? skull.]
1. (Physiol.) Partial or total absence of the skull.
2. pl. (Zo["o]l.) The lowest group of Vertebrata, including
the amphioxus, in which no skull exists.
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