492 Evolution and Distribution of Fishes 



where Atherstonia is also known. But Gyrolepis, Urolepis, 

 and Myriolepis, not only carry the family through the 

 Triassic, they prove that a more or less continuous fresh- 

 water connection had existed from Britain — probably also 

 from N. E. America — through France, S. Germany, Italy 

 and S. Africa as well as N. S, Wales. The persistence of 

 this migrational line into later times is indicated by the 

 finding of species of Coccolepis in Upper Triassic beds of 

 Talbragar in Australia; in Lower Liassic beds of Lyme 

 Regis; in Lower Kimmeridgian of Bavaria; in the Lower 

 Purbeck of S. England; and in all these cases in freshwater 

 deposits. 



The map already referred to (Fig. 23, p. 179), supple- 

 mented by observations for late Carboniferous and Per- 

 mian times, would satisfactorily explain the probable land- 

 connections that aided such distributions. As compared 

 with the maps of Freeh, of de Lapparent, and of Arldt the 

 writer would incline to emphasize a more intimate and 

 direct communication between the North-Atlantis and Eura- 

 sian continents on the one hand, and the Gondwana conti- 

 nent on the other. But of the river, lake, or flood-plain 

 conditions that existed over these we are as yet ignorant. 

 This by no means implies, however, that such knowledge 

 may not yet be got. For if careful note be made — as has 

 already been done in a few cases — of the attitude assumed 

 and the direction to the strata of the fossilized fishes; of the 

 position, consistence and size of the accompanying plant 

 remains; of the trend in deposition of the strata; and the 

 relative perfection of the organisms; in other words, the 

 general ecological bearing of all recognisable factors, much 

 may yet be learned that undoubtedly will greatly extend 

 our knowledge. 



Unless vestiges of them are discovered later over a wider 

 areas than now known, it would seem that the Platysomidae 

 remained more restricted in distribution than did the 

 Palaeoniscidae. According to present knowledge they 

 gradually spread during early Carboniferous time from a 

 primitive centre of evolution that included Ireland, Scot- 

 land, and Belgium. Thence they migrated from late 



