BRACHIOPOD A—THOMSON. 
57 
Australia). While it is still possible that these small forms will turn up in the former 
districts, it appears more probable that they formed an endemic element in the 
Oligocene-Miocene of New Zealand and Australia, and never attained a southern 
circum-Pacific distribution. On the other hand these genera are also found in the 
Indian Ocean and the Mediterranean, viz., Argyrotheca and Amphithyris in the 
Mediterranean, Megerlina at the Island of St. Paul, and Kraussina in South Africa and 
the Indian Ocean. This distribution suggests that Australia had former connections 
with South Africa and the Mediterranean. This probability will be greatly strengthened 
if the generic groupings suggested in the first part of this paper are substantiated, viz., 
the grouping on the one hand of the Mediterranean and Marion Island Platidia with 
Amphithyris and Argyrotheca, and on the other of the Mediterranean Muhlfeldtia, the 
Indian Ocean Kingena, and the Australian Aldingia with Kraussina and Megerlina. 
Argyrotheca occurs in the Eocene of North America and in the Miocene of 
Europe, Platidia and Muhlfeldtia in the Miocene of Europe, and Kingena in the 
Cretaceous of Europe. All the above-mentioned genera, therefore, except Amphithyris 
and Kraussina, are at least as old as the Miocene, and it is probable that these two 
primitive genera are at least Cretaceous if not Jurassic. Except for the South African 
and Indian Ocean forms, which exist in districts where no fossil faunas are known, 
the fossil species show that the genera had attained practically their present distribu¬ 
tion by the Miocene at least, and the connections which made this possible were 
probably still older. 
The most obvious explanation of all the above facts is that these two groups 
of the Terebratellidce originated on the coasts of Gondwana land, on the remnants of 
which they now survive, and to which they are almost restricted. Kingena had 
attained the northern coasts of the Tethys by the Cretaceous and Argyrotheca had 
crossed to America by the Eocene, while Platidia probably crossed about the same 
time. Argyrotheca and presumably Amphithyris had crossed from Australia to New 
Zealand by the Oligocene-Miocene. From the considerations that this Gondwana- 
land element did not reach the Antarctic and South America, and that the southern 
circum-Pacific Oligocene-Miocene fauna did not reach South Africa and Marion 
Island, it seems necessary to conclude that the connections between Australia and 
South Africa had broken down before that between Australia and the Oligocene- 
Miocene Pacific via New Zealand or New Caledonia was established, and further that 
before this Gondwana-land element reached New Zealand, the connections between 
that land and the Antarctic had been severed. 
The Recent fauna of the Kerguelen Islands, consisting of Hemithyris, Tere- 
bratella, “ MageMvmia ” and “ Liothyris ” is a typical southern fauna of the circum- 
Pacific type, and is derived without doubt from an Oligocene-Miocene fauna similar 
to those above described. So far as the Recent Brachiopods are concerned, the group 
may have been isolated from all other southern lands since the close of the Miocene, 
and it does not appear to have retained any evidence of a Gondwana-land connection. 
•20218—H Vol. IV, P\rt 3. 
