enteropneusta

from The Century Dictionary.

• A group of animals of uncertain position, related to the tunicates, and constituted by the genus Balanoglossus alone. See cut under Balanoglossus.

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

• noun plural (Zoöl.) A group of wormlike invertebrates having, along the sides of the body, branchial openings for the branchial sacs, which are formed by diverticula of the alimentary canal. Balanoglossus is the only known genus. See Illustration in Appendix.