THE MARINE FAUNA OF THE BLACKWATER ESTUARY 27
ACARTIIDAE
Acartia clausi Giesbrecht
Not common in the Blackwater plankton. Occurred in
samples taken at the Barrier Wall, Bradwell, July to November
1962 and June to December 1963.
Acartia discaudata (Giesbrecht)
Common in the Blackwater plankton. Occurred in samples
taken at the Barrier Wall, Bradwell, June to September, with a
peak in July-August 1962, and from June to October, with a peak
in July-August 1963.
Acartia bifilosa (Giesbrecht)
Common in the Blackwater plankton.. Occurred in samples
taken at the Barrier Wall, Bradwell; March to November, with
a peak in May 1962, and from April to November with a peak
in April-May 1963.
Acartia tonsa Dana
Rare in the Blackwater plankton. Occurred in samples taken
at the Barrier Wall during 1962 and in May 1963.
Acartia grani G. O. Sars
Rare in the Blackwater plankton in 1962, but recorded in
greater numbers from the low salinity regions of the Blackwater
and the Colne in 1963 and 1964.
LONGIPEDIIDAE
Canuella perplexa Scott
Recorded occasionally in the Blackwater plankton.
Canuella furcigera Scott
Recorded occasionally in the Blackwater plankton.
Harpacticidae
Zaus spinatus Goodsir
Recorded occasionally in the Blackwater plankton.
Peltidiidae
Alteutha interrupta (Goodsir)
A few specimens usually occur in plankton samples taken
during the summer in the Blackwater.
Thalestridae
Parathalestris hibernica (Brady & Robertson)
Some specimens taken from the Blackwater plankton in May
1961.
Tachidiidae
Euterpina acutifrons (Dana)
Common in the Blackwater plankton. Occurred in samples
taken at the Barrier Wall, March to December, with a peak in
September 1962, and throughout the year with a peak in Septem-
ber 1963.