Key to Families of the Order TRICHINELLIDA

1 Digestive tract complete; anus present; vulva near end of oesophagus........................................... 2

- Digestive tract incomplete; anus absent; intestine dilated into sac or modified to form trophosome; vulva near nerve ring.. 3

2 Spicule and spicular sheath present; stichocytes regularly aligned throughout length of oesophagus........... Capillariidae

- Spicule and spicular sheath absent or vestigial; stichocytes irregularly aligned in posterior region of oesophagus................................................................................................ Trichosomoididae

3 Female body divided into thin, anterior region and posterior globular region; stichocytes unicellular; spicule present, spicular sheath poorly developed..................................................................... Cystoopsidae