a. Mouth terminal or subterminal. Family _Enchelinidæ_
Food is swallowed and not
introduced by currents
b. Mouth terminal or subterminal; Family _Trachelinidæ_
body frequently drawn out into
long process; mouth may have
specialized framework.
c. Mouth central or posterior; Family _Chlamydodontidæ_
pharynx with supporting
framework