Summary of Conclusions Reached 519 



distribution were followed, as by the more primitive fishes 

 already examined. But in the early Permian palaeoniscid 

 life received a severe check, and most genera were apparent- 

 ly obliterated, owing to combined xerophytic and volcanic 

 action. Thus Amblypterus and Pygopterus appeared and 

 again disappeared during deposit of this system. Other 

 and doubtless descendant genera like Centrolepis and Coc- 

 colepis first occur in Lower Lias beds, and the latter persists 

 into beds of the Kimmeridge Clay. Special interest attaches 

 to Coccolepis australis found in the Talbragar beds of N. 

 S. Wales, that are regarded as of Jurassic age. Wood- 

 ward says of the fishes: "these are crowded together in 

 shoals as if suddenly destroyed, and very few of these have 

 become disintegrated before fossilization." Here as in 

 many other like cases the author considers that they were 

 killed and covered over by volcanic dust. 



From the more ancient Palaeoniscidae, the divisions 

 Platysomidae and Catopteridae seem to have diverged, as 

 evolving types during the Carboniferous and on to Liassic 

 days. These also have representative species distributed 

 from Connecticut and Virginia on the west, to Austria and 

 thence even to S. Africa and N. S. Wales. Elipsopholis 

 of Woodward seems to be a highly modified and far-travell- 

 ed type, which like the others lived in freshwaters. The 

 liassic genera Chondrosteiis and Gyrosteus show affinities 

 with modern sturgeons, and along with scant remains of 

 Acipenser in Coenozoic (Neobiotic) strata, connect the 

 ancient chondrosteans with existing sturgeons. Species of 

 the last are still largely freshwater, others are anadromous, 

 but none are strictly marine. All however ascend rivers 

 in order to spawn, an ancestral habit that is powerfully re- 

 tained. 



The recent and wholly freshwater genera Scaphirhyn- 

 chiis and Kessleria, that are known as the shovel-nosed 

 sturgeons are now found in rivers of N. America and of 

 Central Asia. This indicates a former land connection be- 

 tween the two continents, a position that abundant distribu- 

 ional facts verify. They are probably a divergent and 

 specialized offshoot from primitive sturgeons. But there 

 also segregated off from small primitive sturgeons, the 



