1. Geniculate acicular chaetae on thoracic chaetiger 6........................................................... 2
- Geniculate acicular chaetae on thoracic chaetigers 5 and 6.................................. T. bigeniculatus sp. nov.
2. Chaetigers 1 to 4 ventrally whitish................................................................. T. gracilis
- Chaetigers 1 to 4 of same coloration as the following......................................................... 3
3. Branchial lobes fused; a large species (body up to 50 mm long)......................................... T. stroemii
- Branchial lobes free; a small species (body less than 20 mm long)........................................ T. atlantis