Key to species of Composetia recorded from Japan

1 Notopodial prechaetal lobe present in anterior chaetigers..........................................2

– Notopodial prechaetal lobe absent throughout.......3

2 Jaws with three teeth in basal half separated by wide interval from double tooth near apical fang; 5 paragnaths in longitudinal series in area I............. C. moorei

– Jaws with four teeth without separated double tooth; 0 or 1 paragnath present in area I............ C. costae

3 Neuropodial heterogomph spinigers absent throughout.................................... C. hircinicola

– Neuropodial heterogomph spinigers present throughout............................................4

4 Heterogomph spinigers present among upper neurochaetae around chaetiger 5... C. tokashikiensis sp. nov.

– Heterogomph spinigers absent among upper neurochaetae throughout............. C. kumensis sp. nov.