cirrostomi

from The Century Dictionary.

• One of the many names applied to the acranial vertebrates (Pharyngobranchia, Leptocardia, or Acrania) represented by the genus Amphioxus or Branchiostoma, the lancelets: so named from the cirri surrounding the mouth.

from the GNU version of the Collaborative International Dictionary of English.

• noun plural (Zoöl.) The lowest group of vertebrates; -- so called from the cirri around the mouth; the Leptocardia. See amphioxus.