ANTAROTIC BENTHOS
97
immediate contact with South America through the Scotia Arc (a route
by which it seems obvious that faunal elements are being added to
Antarctica). The area comprising the Bellingshausen Sea, the Antarctic
Peninsula and the Weddell Sea was therefore disregarded and attention
was focused upon the molluscs of what is essentially East Antarctica.
The benthic molluscs from this area comprise 309 species grouped
in 154 genera and 91 families. Fifty of these families contain only one
Antarctic species, and many are represented by minute, anomalous or
deep-water genera only. Thus the Mytilidae contains only the small,
deep-water genus, Dacrydium and the Arcidae only the small, deepwater, Bathyarca. Only five families contain more than 11 species
(which is the average number for New Zealand). The restricted nature
of the fauna may perhaps be best appreciated by comparing the number
of families, genera and species of Antarctic mollusca with those from
the Magellanic Region or with New Zealand and the same figures for
bivalves alone from these areas and from the Panamic Region.
Comparative figures for the faunas of East Antarctica, the Magellan
Region and New Zealand (Dell, 1964b, 1969).
TABLE IV
Families
Benthic Molluaca
East Antarctica
91
Magellanic Region
114
New Zealand
160
Bivalves
East Antarctica
Magellanic Region
New Zealand
Panamic (Nicol, 1967)
25
39
44
46
Genera
Species
154
309
280
667
552
1,759
36
66
89
175
142
400
147
555
These figures may be used to derive the average number of genera
per family and the average number of species per family and per genus.
It is thus obvious that the Antarctic molluscan fauna is an imbalanced one even compared with a small isolated biological entity like
New Zealand.
The writer (Dell, 1968) has presented the results of the analysis of
the bathymetric distributions of 303 species of Antarctic mollusca for
which reasonable data were available. Only 41 of these molluscs are
confined to depths shallower than 180 m (a generous estimate for the
97
immediate contact with South America through the Scotia Arc (a route
by which it seems obvious that faunal elements are being added to
Antarctica). The area comprising the Bellingshausen Sea, the Antarctic
Peninsula and the Weddell Sea was therefore disregarded and attention
was focused upon the molluscs of what is essentially East Antarctica.
The benthic molluscs from this area comprise 309 species grouped
in 154 genera and 91 families. Fifty of these families contain only one
Antarctic species, and many are represented by minute, anomalous or
deep-water genera only. Thus the Mytilidae contains only the small,
deep-water genus, Dacrydium and the Arcidae only the small, deepwater, Bathyarca. Only five families contain more than 11 species
(which is the average number for New Zealand). The restricted nature
of the fauna may perhaps be best appreciated by comparing the number
of families, genera and species of Antarctic mollusca with those from
the Magellanic Region or with New Zealand and the same figures for
bivalves alone from these areas and from the Panamic Region.
Comparative figures for the faunas of East Antarctica, the Magellan
Region and New Zealand (Dell, 1964b, 1969).
TABLE IV
Families
Benthic Molluaca
East Antarctica
91
Magellanic Region
114
New Zealand
160
Bivalves
East Antarctica
Magellanic Region
New Zealand
Panamic (Nicol, 1967)
25
39
44
46
Genera
Species
154
309
280
667
552
1,759
36
66
89
175
142
400
147
555
These figures may be used to derive the average number of genera
per family and the average number of species per family and per genus.
It is thus obvious that the Antarctic molluscan fauna is an imbalanced one even compared with a small isolated biological entity like
New Zealand.
The writer (Dell, 1968) has presented the results of the analysis of
the bathymetric distributions of 303 species of Antarctic mollusca for
which reasonable data were available. Only 41 of these molluscs are
confined to depths shallower than 180 m (a generous estimate for the