The Dipneusti and Crossopterygii 299 



Britain respectively. But alongside the latter in the Old 

 and New World, evolved the still very imperfectly known 

 genus Palaedaphiis, that for size seems to have rivalled 

 some of the bulky arthrodires. 



As one passes from the Upper Old Red or Devonian 

 to the Calciferous of Scotland, the genera JJronemus and 

 Ctenodus become prominent, while the allied but more 

 ancient Dipteriis and Phaneropleuron disappear. 



But meanwhile a wide invasion of Dipnoans into 

 the Australian section of the Gondwana continent had been 

 effected. For while Newberry described a dipnoan jaw- 

 bone from the freshwater Chemung of America as Gano- 

 rhynchiis beecheri, a closely similar object from the fresh- 

 water Devonian of New South Wales, has been named 

 G. siissmilchii. Further while Ctenodus was still persisting 

 in the Carboniferous of the Europeo-American area, it 

 reached Australia as C. bre-viceps, that was described by 

 Woodward from Victoria. Still later this genus gave off 

 an allied line, Sagenodus, that seems to have been co- 

 existent, over a large part of the world, with the primitive 

 elasmobranch, Pleuracanthus^ not only in Carboniferous, 

 but up even into Permian time. For species typical of both 

 formations extend from Eastern America through N. 

 Europe southward into Australia. 



Once established in Australian lakes and swampy river 

 stretches, the above genera were later replaced bv Gosfor- 

 dia of the Permo-Triassic, and it in turn by Ceratodus dur- 

 ing the early Jurassic, while the existing genus Neocera- 

 todus Is a fairly direct descendant of the last. Woodward, 

 in commenting on this remarkable southern continuity of 

 the Dipnoans (21^: 27 ) , says : "It is thus clear that Dipnoi 

 have always lived in the Australian region, and there is no 

 reason why Ceratodus itself (? Neoceratodus) may not 

 have evolved there." If one were to add after "region" 

 in the above quotation, the phrase "since late Devonian 

 time" the statement would be appropriate, but the existence 

 of Dipterus in the lowest Old Red Rocks of Europe, pos- 

 sibly even the extension backward of dipnoans into the 

 Upper Silurian of Bohemia as Gompholepis and Dipnoites 

 strongly indicate that primitive evolution of Dipneusti may 



