Dichotomous Key/Hirudinea

1

 * Reversible proboscis
 * Present -
 * Not present -

2

 * Teeth
 * Present - Gnathobdellae
 * Not present - Pharyngobdellae

3: Rhynchobdellae

 * Body shape
 * Flat - Glossiphoniidae
 * Cylindrical - Pisciolidae