the marine fauna of the blackwater estuary 25
Serpulidae
Pomatoceros triqueter (Linne)
Empty tubes are generally found on shells and stones on the
bottom and some shores of the Blackwater. Living specimens
are rarely found; Mersea Flat and in dredge samples from Colne
Bar (May 1965).
Spirorbis borealis Daudin
Not found living in the Blackwater, but empty tubes are some-
times found on algae washed up on the beach at Bradwell,
especially after periods of easterly winds (October 1963).
Class OLIGOCHAETA
Oligochaetes are common in littoral mud; few collections or
specific identifications have been made.
Enchytraeidae
Some unidentified species.
Tubificidae
Clitellio arenarius O. F. Muller
In mud, Bradwell Creek.
Peloscolex benedeni Udekem
Bradwell shore; in mud on the lower shore near Weymark's
Sluice (15.5.1961).
Class HIRUDINEA
Rhynchobdellidae
Pontobdella muricata (Linne)
A large leech occasionally found attached to the bodies of
Thornback Ray (Raja clavata). Sometimes there are two or three
specimens on one fish.
Piscicolidae
Hemibdetta solea (van Beneden & Hesse)
Commonly found on the skin of the Sole (Solea solea) and
being very small often occurring in large numbers on one fish.
Phylum SIPUNCULOIDEA
Some unidentified specimens recorded from Bradwell Creek in
1960, but this is a doubtful record.
Phylum ARTHROPODA
Sub-Phylum CRUSTACEA
Class OSTRACODA
Some specimens were collected alive from the plankton and
also from fine sediments on the lower shore.