Key to all described species of Terebellides from the Northwestern Pacific

1. Branchial lobes free of each other........................................................................ 2

- Branchial lobes at least partially fused along their length..................................................... 3

2. Acicular uncini present on TC6 and TC7, lower lip greatly expanded, branchial lobes equal in size................................................................................................ Terebellides intoshi Caullery, 1915

- Acicular uncini on TC6 only, lower lip not expanded, branchial lobes differ in size...................................

............................................................... Terebellides lineata Imajima & Williams, 1985 3. Acicular uncini present on TC5 and TC6............................................. Terebellides ectopium n. sp.

- Acicular uncini on TC6 only.............................................................................4

4. Branchia anteriorly prolonged (5th lobe)................................................................... 5

- Branchia not anteriorly prolonged......................................................................... 6

5. Notopodia of TC1 and TC2 well developed, lateral lappets until TC6.................... Terebellides kobei Hessle, 1917

- Notopodia of TC1 and TC2 markedly less developed than subsequent ones, lateral lappets until TC7..................................................................................................... Terebellides yangi n. sp.

6. Notopodia of TC1 and TC2 well developed......................... Terebellides horikoshii Imajima & Williams, 1985

- Notopodia of TC1 and TC2 markedly less developed than subsequent ones........................................ 7

7. Lateral lappets until TC4 only. Acicular uncini sharply bent with mucronate tips..................................................................................................... Terebellides brevis Imajima & Williams, 1985

- Lateral lappets until TC5 only. Acicular uncini sharply bent without mucronate tips................................. 8

8. Length ratio of thorax and abdomen>1.0, thoracic neuropodia with few (less than 25) uncini per torus, ±40 abdominal seg- ments................................................................... Terebellides guangdongensis n. sp.

- Length ratio of thorax and abdomen almost 0.5, thoracic neuropodia with 40 or more uncini per torus, 45-50 abdominal seg- ments.................................................................... Terebellides japonica Moore, 1903