The systematics of species assigned to the genus
Prionospio Malmgren, 1867 (subgenus
Minuspio Foster, 1971) are confused due to the uncertainty concerning the characteristics of
Prionospio cirrifera Wirén, 1883. Examination of northern European material has demonstrated the presence of
P. cirrifera and another species, at present indistinguishable from
Prionospio multibranchiata Berkeley, 1927. Detailed decriptions of both species are given with a discussion of their zoogeography.
The status of related and synonymised species is examined and it is suggested that specimens of '
P. cirrifera' from all localities be reexamined. Accurate identification would be greatly aided by a rediscovery and redescription of
P. multibranchiata from the type locality.