102
R. R. DELL
of families extend no farther south than the Falklands and the southern
tip of South America, e.g. Chitonidae, Acanthochitonidae, Anomiidae,
Cardiidae, Mactridae, Condylocardiidae, Lucinidae, Solenidae, Corbulidae, Myidae, Pandoridae, Teredinidae, Acmaeidae and Nassariidae.
Another family, the Olividae, reaches the Burdwood Bank. South
Georgia is the limit for the Veneridae, Tellinidae, Hiatellidae, Calyptraeidae and Retusidae. The chiton family Chaetopleuridae does not
extend farther than the South Orkneys. Five more families have
established themselves on the Antarctic Peninsula or the two seas of
West Antarctica, i.e. Hanleyidae, Ischnochitonidae, Mopaliidae,
Gaimardiidae and Patellidae (Dell, 1964b, 1969).
There seems no doubt that Mollusca have also achieved dispersal in
the reverse direction, widely distributed Antarctic species reaching
different northern limits along the Arc. Some species such as Cadulus
dalli antarcticus are conhed to the continent, the South Shetlands,
South Orkneys and South Sandwich Islands. A very large group
reaches as far north as South Georgia, e.g. Adacnarca, Pseudokellya,
Propeleda, L-imatula hodgsoni, Limqsis lilliei, Philobrya sublaevis,
Lissarca notorcadensis, Cyclocardia astartoides, Laternula elliptica,
Cuspidaria infelix and C. tenella. Some Antarctic species reach the
Falkland Islands but do not occur on the mainland of South America,
e.g. Cyamiomactra laminifera and Thracia meridionalis. Four other
Antarctic species which reach their northern limit here have not as yet
been recorded from South Georgia and may be presumed to have crossed
the Drake Passage more directly, Nuttalochiton mirandus, Dentalium
majorinum, Limopsis marionensis and Cyamiocardium denticdatum
(although the last three species also reach southern South America).
Several Antarctic species extend t o the South America mainland,
Yoldia (Aequiyoldia) eightsi, Lepidopleurus kerguelensis, Callochiton
T ~ L E
VI
Total number
of species
Percentage of
Eaat Antarctic
forms
(%)
South Georgia
47
South Orkneys
29
South Sandwich Islands
10
South Shetlrtnds
29
Antarctic Peninsula
31
Bouvet Island
8
42
48
90
68
71
82
R. R. DELL
of families extend no farther south than the Falklands and the southern
tip of South America, e.g. Chitonidae, Acanthochitonidae, Anomiidae,
Cardiidae, Mactridae, Condylocardiidae, Lucinidae, Solenidae, Corbulidae, Myidae, Pandoridae, Teredinidae, Acmaeidae and Nassariidae.
Another family, the Olividae, reaches the Burdwood Bank. South
Georgia is the limit for the Veneridae, Tellinidae, Hiatellidae, Calyptraeidae and Retusidae. The chiton family Chaetopleuridae does not
extend farther than the South Orkneys. Five more families have
established themselves on the Antarctic Peninsula or the two seas of
West Antarctica, i.e. Hanleyidae, Ischnochitonidae, Mopaliidae,
Gaimardiidae and Patellidae (Dell, 1964b, 1969).
There seems no doubt that Mollusca have also achieved dispersal in
the reverse direction, widely distributed Antarctic species reaching
different northern limits along the Arc. Some species such as Cadulus
dalli antarcticus are conhed to the continent, the South Shetlands,
South Orkneys and South Sandwich Islands. A very large group
reaches as far north as South Georgia, e.g. Adacnarca, Pseudokellya,
Propeleda, L-imatula hodgsoni, Limqsis lilliei, Philobrya sublaevis,
Lissarca notorcadensis, Cyclocardia astartoides, Laternula elliptica,
Cuspidaria infelix and C. tenella. Some Antarctic species reach the
Falkland Islands but do not occur on the mainland of South America,
e.g. Cyamiomactra laminifera and Thracia meridionalis. Four other
Antarctic species which reach their northern limit here have not as yet
been recorded from South Georgia and may be presumed to have crossed
the Drake Passage more directly, Nuttalochiton mirandus, Dentalium
majorinum, Limopsis marionensis and Cyamiocardium denticdatum
(although the last three species also reach southern South America).
Several Antarctic species extend t o the South America mainland,
Yoldia (Aequiyoldia) eightsi, Lepidopleurus kerguelensis, Callochiton
T ~ L E
VI
Total number
of species
Percentage of
Eaat Antarctic
forms
(%)
South Georgia
47
South Orkneys
29
South Sandwich Islands
10
South Shetlrtnds
29
Antarctic Peninsula
31
Bouvet Island
8
42
48
90
68
71
82