Key to species of Philometroides

1 Caudal, ventro-lateral, hypodermal extensions present; cuticle of both males and females covered with bosses; worms occur mainly in pectoral fins and occasionally in pelvic, dorsal and anal fins.................................. P. huronensis

- Caudal hypodermal extensions absent; bosses absent from cuticle of males; worms occur mainly in subcutaneous tissues of head...................................................................................... P. nodulosus