n.
Any of various small, flattened marine organisms of the subphylum Cephalochordata, structurally similar to the vertebrates but having a notochord rather than a true vertebral column. Also called amphioxus.
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.