trachystomata

from The Century Dictionary.

• noun A group of urodele amphibians, of eel-like form and without hind legs, as the Sirenidæ.

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

• noun plural (Zoöl.) An order of tailed aquatic amphibians, including Siren and Pseudobranchus. They have anterior legs only, are eel-like in form, and have no teeth except a small patch on the palate. The external gills are persistent through life.