206
THE ESSEX NATURALIST
Helicotylenchus sp.
Sample 6 (non-brackish soil).
Metachromadora remand Gerlach, 1951.
Sample 5. Apparently only previously known from the type localities
(north-west coast of Germany).
Monachus (Anatonchus) tridentatus (de Man, 1876).
Sample 6.
Oxydirus oxycephaloides (de Man, 1921).
Sample 6.
Plectus granulosus Bastian, 1865.
Sample 6.
Sabatiera sp.
Sample 5.
Sphaerolaimus gracilis de Man, 1876.
Sample 5. Although a well known European form, it has not been
reported from Britain before.
Spilophorella paradoxa (de Man, 1888).
Sample 5.
Symplocostoma sp.
Sample 5.
Terschellingia communis de Man, 1888.
Sample 5. Not reported from Britain before.
Theristus (Cylindrotheristus) oxycerca (de Man, 1888).
Sample 5. Found recently in sand at Whitstable (Maghraby and Per-
kins, 1956).
Theristus (Penzanzia) fluvensis Schuurmans Stekhoven, 1935
(—Theristus velox de Man, 1921 nec Bastian, 1865).
Samples 2, 3, 4 and 5. This species does not appear to have been
reported from Britain before.
Theristus (Trichotheristus) setosus (Butschlli, 1874).
Sample 1.
The brackish samples are fairly rich in individual nematodes, although
only a few species are represented. Two of these (Adoncholaimus thalas-
sophygas and Dichromadora geophila) are forms described by J. G. de
Man (1876) from soil soaked with brackish water on the Island of
Walcheren (Holland). The sea wall on Skippers Island is broken and a
large part of the Island is flooded during high tides, and this has led
to conditions similar to those found on Walcheren.
The predatory nematode, Adoncholaimus thalassophygas is common
to all the samples examined with the exception of that from non-
brackish soil (sample 6) where it is replaced by another predatory
species, Morionchus (Anatonchus) tridentatus, originally found in moist
soil in Holland and Germany and since reported as widespread in
Europe.