' RECENT BRACHIOPODA 275 



tella harrettiana, dredged off Eio de Janeiro. Of deep-sea migrants into 

 the tropical Atlantic are Chlidonophora incerta (on the equator in mid- 

 ocean) and Pelagodiscus atlanticus (1 degree north, 24 degrees west). 

 Mediterranean relicts, as Liothyrina vitrea and Dyscolia wyvilii, occur to 

 the north of the region designated — that is, on the Cape Verde Islands. 



From the Antarctic region have come the 3 migrants Liothyrina uva 

 (north to Eio de Janeiro), L. wyvillii (Falklands), and the very charac- 

 teristic boreal Bouchardia rosea at Eio de Janeiro. 



In other words, along the shores of eastern South America (5) and off 

 the western coast of Africa (1) are found but 6 species, there being 2 

 others in the deep sea and 4 relicts on oceanic islands, one of which 

 occurs also off Brazil. 



This survey of brachiopod distribution shows clearly not only the 

 former existence of equatorial Gondwana across the Atlantic, but as well 

 that its vanished Atlantic bridge still controls the distribution of living 

 forms. We see that the genera of the northern Atlantic (Poseidon) dis- 

 tributed themselves in one direction, more or less widely throughout the' 

 northern hemisphere and in another pathway eastward into the Indian 

 Ocean by way of the northern shore of Gondwana, but the main drift was 

 far more decidedly westward along the same land by way of the Antillean 

 region into the Pacific, and thence in the main down the west coast of 

 South America into the Antarctic realm. Gondwana appears to have 

 existed until middle Eocene times; the deciding land barrier between 

 the fauna of the northern and southern hemispheres and the inter- 

 hemisphere shallow-water genera followed either its shores or those of 

 Oceanica and the northern Pacific bounding lands. What is true regard- 

 ing the dispersion of brachiopods will probably be found essentially 

 similar for other groups of animals with short non-feeding larval stages 

 and inhabiting equatorial waters. 



8TRAT1QRAPH1G SIGNIFICANCE OF OSTRACODA^ 

 BY R. S. BASSLER 



The recent bivalved crustaceans falling under the order Ostracoda are 

 world-wide in their distribution both in fresh and salt waters. Not only 

 are many of the species properly termed cosmopolitan, but they are also 

 apparently unlimited bathymetrically. Today we find them swimming 

 at the surface or creeping over the bottom in great colonies, and after the 



» Manuscript received by the Secretary of the Society May 23, 1911. 



