Source : Webster's Revised Unabridged Dictionary (1913)

Cirrostomi \Cir`ros"to*mi\, n. pl. [NL., fr. E. cirrus + Gr. ?
   mouth.] (Zo["o]l.)
   The lowest group of vertebrates; -- so called from the cirri
   around the mouth; the Leptocardia. See {Amphioxus}.