THE OPALINID CILIATE IXFUSOBIANS. 307 



Equatorian continent again separated into two parts (fig. 233) : 

 'Australia parting from the lands to the west and forming instead a 

 temporary connection to the north with Asia-Malaysia ; and South 

 Atlantis being reestablished, but with a Madagascar-India extension 

 to the northeast across the Indian Ocean. There was connection be- 

 tween Antarctica and both Australasia and Patagonia after this 

 Jurassic division of Equatoria during the early Tertiary (fig. 236), 

 and perhaps also during one or more earlier periods, though this is 

 not shown in the charts except for the late Cretaceous (fig. 235, A) . 

 During the Cretaceous (figs. 234 and 235, A) Africa separated from 

 South America, and at about the same time, or perhaps not until 

 the early Tertiary (fig. 236), the Africa-Madagascar-Seychelles- 

 India bridge became broken up. 3. There have been certain North 

 Temperate and Arctic land masses variously interconnected at dif- 

 ferent periods, being completely imited during most of the Tertiary 

 and during the Quaternary glacial periods (figs. 236, 237, 238). 

 Schuchert (1915?) shows early Permian connections between all con- 

 tinents — Antarctica being united to Australia and South America; 

 Equatoria being broadly connected with Europe ; and Europe, Green- 

 land, North America, and Asia all being united into one continuous 

 North Temperate and Arctic land mass. But Ave are not carrying 

 our discussion of the Anura and the Opalinidae back to the Permian. 

 We have no indication of their existence at that time. This northern 

 land mass, Arctogea, during the middle Tertiary (fig. 237) estab- 

 lished connections with the chief remnants of Equatoria (South 

 America, Africa, India, Malaysia [a part of Equatoria in earlier 

 periods but not in Triassic times], but not Australia), and it has re- 

 tained these connections (fig. 238). 



These opinions expressed in the charts used are accepted without 

 criticism as a basis of our present discussion. Even though the paleo- 

 geographic conclusions are still under consideration, there is suffi- 

 cient general agi'eement on the major features to make it important 

 to align these tentative conclusions with the data in the present paper 

 and to see what suggestions and implications, or even conclusions, 

 may result; and, for the sake of illustrating the host-parasite 

 method of studying zoogeographical and related questions, we will 

 accept and use even the details in the paleogeographic charts chosen. 

 Cnir discussion is therefore largely of the nature of a preliminary 

 review of the data, subject to later critical emendation. 



Of course, in any " geologic period," covering as it did millions of 

 years, there were geographic changes. No series of charts, in the pres- 

 ient state of our knowledge, can be expected to show these changes in 

 detail, and we are not even using the most detailed charts available,but 

 are using rather a series of maps which are broad generalizations, omit- 



