THE MARINE FAUNA OF THE BLACKWATER ESTUARY 53
Amphiuridae
Acrocnida branchiata (Montagu)
On the lower shore at Bradwell (2.2.1962). May be common
as one of the many ophiuroids collected from the Blackwater
benthos but not identified.
Ophiolepidae
Ophiura texturata Lamarck
Identified from among ophiuroids collected by dredge on
bottoms of sandy mud at the mouth of the Blackwater and off-
shore.
Ophiura albida Forbes
Identified from among ophiuroids collected by dredging on
bottoms of sandy mud at the mouth of the Blackwater and
offshore.
Ophioglypha ciliata Muller
Recorded from the Blackwater by the Essex Field Club excur-
sion of September 1888 (Cole). May be synonymous with one of
the species of ophiuroid given above.
Class ECHINOIDEA
Order Diadematoidea
ECHINIDAE
Psammechinus miliaris (Gmelin)
Not an important member of the benthos within the Black-
water but common in offshore waters. Cole (1888) gives records
of specimens taken in dredge hauls within the Blackwater, and
Orton and Lewis (1931) indicate that it was abundant in Thirslet
Creek in 1913 but rare after the 1914-18 war. It is suggested that
mortalities may have occurred as a result of the severe winter of
1916-17. Records from recent investigations are restricted to the
mouth of the Blackwater and offshore areas. During May-June
1962, specimens were commonly found at Swin-Spitway, North
Eagle, Colne Bar, Knoll, Wallet Channel and North Buxey Beacon.
Dredge hauls taken on 'ross' ground could contain up to twelve
specimens. The species was still present in these areas in 1963
showing no deleterious effects from the severe winter.
Echinus sphaera (Muller)
Recorded by the Essex Field Club excursion of 1888 (Cole,
1888).
Class HOLOTHUROIDEA
Holothurians were recorded as abundant by the Essex Field
Club in 1888. Recently, occasional specimens have been obtained
in dredge samples from the Thirslet area. No specific identifica-
tions have been made.