218
WILLIAM MACNAE
Potamididae and the Ellobiidae. Two other families are represented by
one or two species : the Onchidiidae and Littorinidae.
The littorinids are forms which live among the foliage of the trees of
Avicennia and Xonneratia in the landward fringe. Littorina (Melarapha)
scabra is widespread in the Indo-Pacific; feeding probably on the
colonies of algae which grow on the twigs and older leaves, they do not
seem to chew the leaves on which they are often found. The bivalve
Enigmonin ro+sea is a suspension feeder (Yonge, 1957).
Peronia peroni (Cuv.) is the common onchidiid in eastern Africa and
Madagascar and other species replace it elsewhere.
The family Potamididae is represented by a series of species and
genera. Pyrazus ebeninus J. E. Gray is a characteristic inhabitant of
mud flats below mean sea-level but may occasionally extend upwards
among the lowermost pneumatophores of the seaward fringe on stable
shores with neither accretion nor erosion. Terebralia palustris and T .
sulcata, almost sympatric species, live on the surface of firmer muds in
the seaward fringes and bruguiera forests but are absent from the
soft muds of the rhizophora forests. Telescopiurn telescopium is
characteristically found on soft muds in the rhizophora forests, on the
surface of the mud in shallow pools, and on the muddy banks of
creeks. T . rnauritsi lives on the firmer muds of the sonneratia and
avicennia fringes in Java and Sumatra (Butot, 1954). I n Malaya it
is almost sympatric with the other, both being commonly found
together.
The ellohiids are commonest at the upper level of the bruguiera
forest, in ceriops thickets and under the litter of the landward fringes.
This family, which Morton (1955) considers to be the most primitive of
the pulmonates, has representatives of several genera in the mangal
fauna : Ophicardelus, Melampus, Cassidula, Ellobiurn and Pythia are all
represented by several species. Of these Pythia is the most terrestrial,
its species ranging from the upper levels of the landward fringe into the
rain forest above high water mark. Ophicardelus and Melampus are
cryptic forms living under the leaves, logs, etc. which litter the surface
of the landward fringes. Cassidula and Ellobiurn are more characteristic
of the lower levels of the landward fringe and extend downwards
almost to the seaward edges of the bruguiera and rhizophora forests.
Melampus still possesses a free-swimming veliger but this is suppressed
in the others. To some extent these molluscs are responsible for
reducing fallen leaves to humus. Although they are recorded as living
on the slimy mud around the mangrove roots and pneumatophores,
species of Cassidula and Ellobiurn are usually found where fallen leaves
are coinmon. Ophicardelus and MelamrLpus are normally cryptic occur-
WILLIAM MACNAE
Potamididae and the Ellobiidae. Two other families are represented by
one or two species : the Onchidiidae and Littorinidae.
The littorinids are forms which live among the foliage of the trees of
Avicennia and Xonneratia in the landward fringe. Littorina (Melarapha)
scabra is widespread in the Indo-Pacific; feeding probably on the
colonies of algae which grow on the twigs and older leaves, they do not
seem to chew the leaves on which they are often found. The bivalve
Enigmonin ro+sea is a suspension feeder (Yonge, 1957).
Peronia peroni (Cuv.) is the common onchidiid in eastern Africa and
Madagascar and other species replace it elsewhere.
The family Potamididae is represented by a series of species and
genera. Pyrazus ebeninus J. E. Gray is a characteristic inhabitant of
mud flats below mean sea-level but may occasionally extend upwards
among the lowermost pneumatophores of the seaward fringe on stable
shores with neither accretion nor erosion. Terebralia palustris and T .
sulcata, almost sympatric species, live on the surface of firmer muds in
the seaward fringes and bruguiera forests but are absent from the
soft muds of the rhizophora forests. Telescopiurn telescopium is
characteristically found on soft muds in the rhizophora forests, on the
surface of the mud in shallow pools, and on the muddy banks of
creeks. T . rnauritsi lives on the firmer muds of the sonneratia and
avicennia fringes in Java and Sumatra (Butot, 1954). I n Malaya it
is almost sympatric with the other, both being commonly found
together.
The ellohiids are commonest at the upper level of the bruguiera
forest, in ceriops thickets and under the litter of the landward fringes.
This family, which Morton (1955) considers to be the most primitive of
the pulmonates, has representatives of several genera in the mangal
fauna : Ophicardelus, Melampus, Cassidula, Ellobiurn and Pythia are all
represented by several species. Of these Pythia is the most terrestrial,
its species ranging from the upper levels of the landward fringe into the
rain forest above high water mark. Ophicardelus and Melampus are
cryptic forms living under the leaves, logs, etc. which litter the surface
of the landward fringes. Cassidula and Ellobiurn are more characteristic
of the lower levels of the landward fringe and extend downwards
almost to the seaward edges of the bruguiera and rhizophora forests.
Melampus still possesses a free-swimming veliger but this is suppressed
in the others. To some extent these molluscs are responsible for
reducing fallen leaves to humus. Although they are recorded as living
on the slimy mud around the mangrove roots and pneumatophores,
species of Cassidula and Ellobiurn are usually found where fallen leaves
are coinmon. Ophicardelus and MelamrLpus are normally cryptic occur-