TrachystomataTra`chy*stom"a*ta\, n. pl. [NL., fr. Gr. ? rough + stoma.] (Zo["o]l.) 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.