from the GNU version of the Collaborative International Dictionary of English
- n.pl. The lowest class of Vertebrata, including only the Amphioxus. The heart is represented only by a simple pulsating vessel. The blood is colorless; the brain, renal organs, and limbs are wanting, and the backbone is represented only by a simple, unsegmented notochord. See amphioxus.
from The Century Dictionary and Cyclopedia
- Same as Leptocardii.
Sorry, no etymologies found.