1	Dorsal cirri distinctly flattened	Myrianida pinnigera (Montagu, 1808) (1, 5)
–	Dorsal cirri cylindrical	2
2	Pharynx with several sinuations	3
–	Pharynx with 1–2 sinuations	4
3	Cirrophores swollen; cirrostyles attached subterminally on cirrophores. Trepan with indistinct teeth	Myrianida inermis (Saint-Joseph, 1886) (5)
–	Cirrophores not swollen; cirrostyles attached terminally on cirrophores. Trepan with 9 distinct teeth	Myrianida convoluta (Cognetti, 1953) (1, 5)
4	Cirrophores on both short and long cirri longer than cirrostyles in median chaetigers	Myrianida sanmartini Dietrich, Hager, Bönsch, Winkelman, Schmidt & Nygren, in press (17)
–	Cirrophores on at least short cirri shorter than cirrostyles in all chaetigers	5
5	Teeth of trepan unequal	6
–	Teeth of trepan all of equal size	8
6	Colour pattern of 4 red spots on each segment. Trepan with 30–35 unequal teeth, 4–5 large and 26–30 small	Myrianida rubropunctata (Grube, 1860) (5)
–	Not as above	7
7	Trepan with 22–29 teeth, alternating 1 large and 1-3 short	Myrianida brachycephala (Marenzeller, 1874) (1, 5)
–	Trepan with 4–5 large teeth and 25–39 short	Myrianida langerhansi (Gidholm, 1967) (5)
8–	Trepan with 12–24 teeth	Myrianida quinquedecimdentata (Langerhans, 1884) (1, 5)
–	Trepan with 24–34 teeth	9
9	Cirri with more or less distinct alternation in length along body. Cirrophores on long cirri slightly longer than parapodial lobes	Myrianida prolifera (O. F. Müller, 1788) (1, 5)
–	Cirri similar along body. Cirrophores on long cirri equal to parapodial lobes	Myrianida edwardsi (Saint-Joseph, 1886) (1, 5)