Key to species of Glyphanostomum

1. Median gap between left and right group of branchiae absent ............................... Glyphanostomum holthei sp. nov.

- Median gap between groups of branchiae present........................................................................................................ 2

2. Branchiae of each group in oblique row........................................................................... Glyphanostomum scotiarum

- Branchiae in straight row across dorsum...................................................................................................................... 3

3. Narrow median gap between groups of branchiae. One pair of eye-spots present............. Glyphanostomum abyssale

- Wide median gap between groups of branchiae. No eye-spots ....................................... Glyphanostomum pallescens