Key to European species of Trichobranchidae

1A. One large branchia with transverse lamellae.....................................................2 ( Terebellides)

1B. Two or three pairs of branchiae...........................................................14 ( Trichobranchus)

1C. Four pairs of branchiae................................................................... 16 ( Octobranchus)

2A. Geniculate acicular chaetae on TC5 and TC6................................................... T. bigeniculatus

2B. Geniculate acicular chaetae on TC6 only................................................................... 3

3A. Branchial lamellae margins without papillae................................................................ 4

3B. Branchial lamellae margins with papillae................................................................. 11

4A. Lower branchial lobes with long filaments................................................................. 5

4B. Lower branchial lobes without or with short projections...................................................... 6

5A. Glandular region on TC3 present; branchial lamellae pointed; notochaetae from TC1 longer than following ones; dorsal papil- lae absent.............................................................................. T. parapari n. sp.

5B. Glandular region on TC3 absent; branchial lamellae rounded; all notochaetae equal-sized; dorsal papillae present................................................................................................... T. shetlandica

6A. Ventral white band on TC4 after MG staining present......................................................... 7