hemichordate

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various wormlike marine animals of the phylum Hemichordata, having gill slits and a structure similar to a notochord.

from The Century Dictionary.

• Partly chordate. as the anomalous genus Balanoglossus.
• noun A hemichordate animal.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun biology Any of many marine worms, of the phylum Hemichordata, that have a primitive notochord
• adjective Of, pertaining to, or characteristic of these animals