a. Two series of teeth in the lower jaw.
α. Quadrato-jugal in contact with parietal.
Tentacle behind nostril; end of body laterally compressed.
Typhlonectes, 3 species, America, p. [93].
β. Quadrato-jugal separated from parietal.
Tentacle between eye and nostril.
Chthonerpeton, 2 species, America.
b. One series of teeth.
α. Quadrato-jugal and parietal in contact; tentacle in front of the eye.
Siphonops, 4 species, America.