ANTARCTIC BENTHOS
105
The most marked feature of the composition of the Antarctic
echinoid fauna is the very sparse family representation. Over 60 families
of echinoids are known. Of these only six families occur in the coastal
waters of Antarctica. The super-orders Diadematacea and Gnathostomata are absent and the only representative of the super-order Echinacea is the genus Sterechinus. On the positive side the cidaroid subfamily Ctenocidaridae and the spatangid family Schizasteridae are
extremely well represented with every indication of radiative evolution.
The subfamily Ctenocidarinae is apparently an ancient group which
developed in Antarctica and has remained almost completely confined
to the Antarctic-Subantarctic area (Mortensen, 1928). Mortensen has
reported an Eocene species of Austrocidaris from Patagonia. The members of this subfamily with a precis of their distribution are given
below.
1. Notocidaris. A genus endemic to the Antarctic, and there represented by six species, N . gaussensis Mortensen, N . hastata Mortensen,
N . mortenseni Koehler, N . platyacanth (H. L. Clark), N . remigera
Mortensen and N . spinosa Koehler. Distribution maps show four
centres of distribution, but these are the usual ones which show up on
Antarctic distribution maps and can only be said to map expeditionary
effort. The species seem largely confined to the Antarctic shelf'. N .
gaussensis broods its young.
2. Ctenociduris. Known only from the Antarctic-Subantarctic, with
six species. The species C. geliberti (Koehler), C . perrieri Koehler, C .
polyplax Mortensen, C. speciosa Mortensen and C. rugosa (Koehler) are
confined to the Antarctic, while C. nutrix (Thomson) is known from
around Kerguelen and off the Crozets. Ctenociduris speciosa is found on
the Antarctic continental shelf' but also extends to South Georgia, the
only representative of the subfamily so far recorded from this latter
locality.
3. Aporocidaris. Two species occur in the Antarctic, one A . incerta
Koehler apparently confined to this area, the other A . untarctica
Mortensen occurring off East Antarctica and also off the Crozets. The
two other known species occur off the Galapagos ( A . milleri (Agassia))
and from the North Pacific (A. fragilis (Agassiz and Clark)), both in
depths over 2 800 m.
4. Bhynchocidaris. The sole species in this endemic genus, R. triplopora Mortensen has been recorded from East Antarctica and from
off the Antarctic Peninsula.
6 . Hornabcidaris. Another endemic Antarctic genus based upon the
sole species, H . gigantea (H. L. Clark), known only from off East
Antarctica.
105
The most marked feature of the composition of the Antarctic
echinoid fauna is the very sparse family representation. Over 60 families
of echinoids are known. Of these only six families occur in the coastal
waters of Antarctica. The super-orders Diadematacea and Gnathostomata are absent and the only representative of the super-order Echinacea is the genus Sterechinus. On the positive side the cidaroid subfamily Ctenocidaridae and the spatangid family Schizasteridae are
extremely well represented with every indication of radiative evolution.
The subfamily Ctenocidarinae is apparently an ancient group which
developed in Antarctica and has remained almost completely confined
to the Antarctic-Subantarctic area (Mortensen, 1928). Mortensen has
reported an Eocene species of Austrocidaris from Patagonia. The members of this subfamily with a precis of their distribution are given
below.
1. Notocidaris. A genus endemic to the Antarctic, and there represented by six species, N . gaussensis Mortensen, N . hastata Mortensen,
N . mortenseni Koehler, N . platyacanth (H. L. Clark), N . remigera
Mortensen and N . spinosa Koehler. Distribution maps show four
centres of distribution, but these are the usual ones which show up on
Antarctic distribution maps and can only be said to map expeditionary
effort. The species seem largely confined to the Antarctic shelf'. N .
gaussensis broods its young.
2. Ctenociduris. Known only from the Antarctic-Subantarctic, with
six species. The species C. geliberti (Koehler), C . perrieri Koehler, C .
polyplax Mortensen, C. speciosa Mortensen and C. rugosa (Koehler) are
confined to the Antarctic, while C. nutrix (Thomson) is known from
around Kerguelen and off the Crozets. Ctenociduris speciosa is found on
the Antarctic continental shelf' but also extends to South Georgia, the
only representative of the subfamily so far recorded from this latter
locality.
3. Aporocidaris. Two species occur in the Antarctic, one A . incerta
Koehler apparently confined to this area, the other A . untarctica
Mortensen occurring off East Antarctica and also off the Crozets. The
two other known species occur off the Galapagos ( A . milleri (Agassia))
and from the North Pacific (A. fragilis (Agassiz and Clark)), both in
depths over 2 800 m.
4. Bhynchocidaris. The sole species in this endemic genus, R. triplopora Mortensen has been recorded from East Antarctica and from
off the Antarctic Peninsula.
6 . Hornabcidaris. Another endemic Antarctic genus based upon the
sole species, H . gigantea (H. L. Clark), known only from off East
Antarctica.