68
R. H. MILLAR
Brewin (1946, 1948, l950b, 105Oc, 1950d, 1051, 1952a, 1952b, 1954,
1957, 1958a, 1958b, 1960). In some cases it is possible to recognize
closely related species with allopatric distribution, as Pyura pachydermatina (Herdman) from the South Island, P . spinosissima Michaelsen from the North Island, and P . chathamensis Brewin from the
Chatham Islands (Brewin, 1952b ; Knox, 1063). Distributions of this
kind may have resulted from past fluctuations in the position of the
boundary between the warm and cold watcr masscs, for which geological evidence exists (Knox, 1963). Other regions of the sea rich in
species may also have been subject to such changcs in hydrographic
boundaries which promotc speciation.
South Africa
The coastal and off-shore waters of South Africa, like those of New
Zealand, are influenced by the proximity of warm and cool currents.
On the east coast the fauna is tropical at least as far south as Durban,
but the south coast from about Algoa Bay to Cape Point supports a
distinct fauna. The third faunistic division is the Namaqua fauna,
occupying the coast from Cape Point to 18"s and is subject to the cool
Benguela Current and to the upwelling of cold deep water.
South African ascidians have been extensively studied, by Hartmeyer (1911, 1912, 1913), Michaelsen (1904, 1915, 1923, 1934) and
Millar (1955a, 1962b, 1964a), and some 84 species may be recognized,
according t o my estimate. A large and representative collection
amounting to 69 species taken from coastal waters between Morrumbene
on the tropical east coast and Saldanha Bay in the southern part of the
Namaqua area showed 39% warm-water, 22% cold-watcr, 4% ubiquitous and 35% south-coast components (Milhr, 1062b). These figures
are in quite good agreement with those of Stephenson (1944) for littoral
animals as a whole. About half of the South African ascidians are
endemic, and the general affinities of this fauna are with the adjacent
areas of the warmer Indian Ocean. There is, however, evidence of some
relationship with the Antiboreal fauna, in the presence of Aplidium
retiforme (Herdman) which also occurs at Kerguelen, Corella eumyota
Traustedt, which is widely distributed in southern waters, and Agnesia
glaciata Michaelsen (Millar, 1962b). The endemic Sycozoa arborescem
Hartmeyer marks the occurrence of a genus characteristic of the
Antarctic, Subantarctic and western Pacific. One may conclude that,
in the main, the South African ascidian fauna has bcen derived from
the Indo-west-Pacific but that a small element originated from the
Antiboreal, possibly in a geological period when the Antiboreal Convergence lay farther north than at present.
R. H. MILLAR
Brewin (1946, 1948, l950b, 105Oc, 1950d, 1051, 1952a, 1952b, 1954,
1957, 1958a, 1958b, 1960). In some cases it is possible to recognize
closely related species with allopatric distribution, as Pyura pachydermatina (Herdman) from the South Island, P . spinosissima Michaelsen from the North Island, and P . chathamensis Brewin from the
Chatham Islands (Brewin, 1952b ; Knox, 1063). Distributions of this
kind may have resulted from past fluctuations in the position of the
boundary between the warm and cold watcr masscs, for which geological evidence exists (Knox, 1963). Other regions of the sea rich in
species may also have been subject to such changcs in hydrographic
boundaries which promotc speciation.
South Africa
The coastal and off-shore waters of South Africa, like those of New
Zealand, are influenced by the proximity of warm and cool currents.
On the east coast the fauna is tropical at least as far south as Durban,
but the south coast from about Algoa Bay to Cape Point supports a
distinct fauna. The third faunistic division is the Namaqua fauna,
occupying the coast from Cape Point to 18"s and is subject to the cool
Benguela Current and to the upwelling of cold deep water.
South African ascidians have been extensively studied, by Hartmeyer (1911, 1912, 1913), Michaelsen (1904, 1915, 1923, 1934) and
Millar (1955a, 1962b, 1964a), and some 84 species may be recognized,
according t o my estimate. A large and representative collection
amounting to 69 species taken from coastal waters between Morrumbene
on the tropical east coast and Saldanha Bay in the southern part of the
Namaqua area showed 39% warm-water, 22% cold-watcr, 4% ubiquitous and 35% south-coast components (Milhr, 1062b). These figures
are in quite good agreement with those of Stephenson (1944) for littoral
animals as a whole. About half of the South African ascidians are
endemic, and the general affinities of this fauna are with the adjacent
areas of the warmer Indian Ocean. There is, however, evidence of some
relationship with the Antiboreal fauna, in the presence of Aplidium
retiforme (Herdman) which also occurs at Kerguelen, Corella eumyota
Traustedt, which is widely distributed in southern waters, and Agnesia
glaciata Michaelsen (Millar, 1962b). The endemic Sycozoa arborescem
Hartmeyer marks the occurrence of a genus characteristic of the
Antarctic, Subantarctic and western Pacific. One may conclude that,
in the main, the South African ascidian fauna has bcen derived from
the Indo-west-Pacific but that a small element originated from the
Antiboreal, possibly in a geological period when the Antiboreal Convergence lay farther north than at present.