Key to species of Cucullanellus

1 Cuticle 0.020-0.050 thick; mouth opening slightly inclined dorsally................................... C. cotylophora

- Cuticle thinner than 0.020; mouth opening transverse to body axis............................................. 2

2 Ventral intestinal caecum not reaching nerve ring.................................................... C. kanabus

- Ventral intestinal caecum reaches nerve ring, its apex sometimes double.................................. C. minutus