94
R. E. DELL
all species of these genera can attach themselves by byssal threads, and
probably all brood the developing young inside the parent shells. The
systematics of the genus Philobrya require critical revision based upon
much better collections than have as yet been available. The writer
(Dell, 1964b) has discussed some of the systematic problems, and pointed
out probable synonyms. Species attach themselves to algae, hydroids
or Bryozoa. The common widely distributed species is Philobrya sublaevis (Pelseneer). The small Adacnarca nitens Pelseneer attaches itself
to hydroids, Bryozoa or sponges (Dell, 1964b), ascidians (Soot-Ryen,
1951), or gorgonaceans (Nicol, 1966). Mortensen (1909) reported it as
attached to the spines of Notocidaris gaussensis Mortensen. A . nitens
is circum-Antarctic in distribution, reaching South Georgia through the
islands of the Scotia Arc. The genus Lissarca is well developed in the
Subantarctic and farther north. The species, L. miliaris (Philippi)
(which may include L . rubrofusca Smith) extends as far south as the
South Shetland Islands. The typical Antarctic species, however, is L.
notorcadensis Melvill and Standen which is circum-Antarctic in its
distribution extending to South Georgia. This species is found attached
to sponges, bryozoans, algae and hydroids, but usually to the spines of
echinoids.
The family Pectinidae is represented by three species of Cyclopecten
and some badly-understood deep-water forms, and the large, circumAntarctic, brightly coloured Adamussium colbecki (Smith), which seems
to occur most commonly in relatively shallow water. The genus contains only the single species and is endemic to the Antarctic.
The family Limidae musters six species of Limatula, some not well
understood. Three groups are obviously represented, the largest in size
L. hodgsoni Smith, well distributed around the Antarctic and as far
north as South Georgia. A group of medium-sized species centres round
L. pygmea (Philippi) and L. ovalis (Thiele), and a small sized species is
L. simillima (Thiele) which obviously belongs to the same group as the
widely distributed L . subauricul ata .
Several families of small bivalves are well represented, e.g. Cyamiidae, Thyasiridae, Leptonidae, Erycinidae, Montacutidae and Neoleptonidae. The family Gaimardiidae is essentially a Subantarctic, coldtemperate group, although a few species reach South Georgia. The
septibranch genus Cuspidaria (Cuspidariidae) has five species, C.
concentrica Thiele, C . infelix Thiele, C . plicata Thiele, C . kerguelensis
(Smith) and C . tenella Smith in Antarctic waters.
Nicol(l970) has summarized the major peculiarities of the Antarctic
bivalves. A very high percentage (61%) are no more than 10 mm in
length along their longest axis. Of the faunas analysed by Nicol the
R. E. DELL
all species of these genera can attach themselves by byssal threads, and
probably all brood the developing young inside the parent shells. The
systematics of the genus Philobrya require critical revision based upon
much better collections than have as yet been available. The writer
(Dell, 1964b) has discussed some of the systematic problems, and pointed
out probable synonyms. Species attach themselves to algae, hydroids
or Bryozoa. The common widely distributed species is Philobrya sublaevis (Pelseneer). The small Adacnarca nitens Pelseneer attaches itself
to hydroids, Bryozoa or sponges (Dell, 1964b), ascidians (Soot-Ryen,
1951), or gorgonaceans (Nicol, 1966). Mortensen (1909) reported it as
attached to the spines of Notocidaris gaussensis Mortensen. A . nitens
is circum-Antarctic in distribution, reaching South Georgia through the
islands of the Scotia Arc. The genus Lissarca is well developed in the
Subantarctic and farther north. The species, L. miliaris (Philippi)
(which may include L . rubrofusca Smith) extends as far south as the
South Shetland Islands. The typical Antarctic species, however, is L.
notorcadensis Melvill and Standen which is circum-Antarctic in its
distribution extending to South Georgia. This species is found attached
to sponges, bryozoans, algae and hydroids, but usually to the spines of
echinoids.
The family Pectinidae is represented by three species of Cyclopecten
and some badly-understood deep-water forms, and the large, circumAntarctic, brightly coloured Adamussium colbecki (Smith), which seems
to occur most commonly in relatively shallow water. The genus contains only the single species and is endemic to the Antarctic.
The family Limidae musters six species of Limatula, some not well
understood. Three groups are obviously represented, the largest in size
L. hodgsoni Smith, well distributed around the Antarctic and as far
north as South Georgia. A group of medium-sized species centres round
L. pygmea (Philippi) and L. ovalis (Thiele), and a small sized species is
L. simillima (Thiele) which obviously belongs to the same group as the
widely distributed L . subauricul ata .
Several families of small bivalves are well represented, e.g. Cyamiidae, Thyasiridae, Leptonidae, Erycinidae, Montacutidae and Neoleptonidae. The family Gaimardiidae is essentially a Subantarctic, coldtemperate group, although a few species reach South Georgia. The
septibranch genus Cuspidaria (Cuspidariidae) has five species, C.
concentrica Thiele, C . infelix Thiele, C . plicata Thiele, C . kerguelensis
(Smith) and C . tenella Smith in Antarctic waters.
Nicol(l970) has summarized the major peculiarities of the Antarctic
bivalves. A very high percentage (61%) are no more than 10 mm in
length along their longest axis. Of the faunas analysed by Nicol the