BUFFALO SOCIETY OF NATURAL SCIENCES 207 



and it is possible that they might have been able to withstand exposure 

 to the air for several hours. In passing from one stream to another 

 their locomotion would be fairly rapid and their migration in this 

 manner might not have been infrequent. 



APPLICATION OF PRINCIPLES DEDUCED FROM MODERN FAUNAL 

 DISTRIBUTION 1 



By the discriminating use of the laws which have been observed 

 to be potent in directing the migration of fishes and other organisms 

 living in the rivers at present, and without making any unwarranted 

 assumptions, it seems safe to postulate the following expectabilities 

 in regard to the geological and geographical distribution which we 

 should be able to find among the eurypterids, providing they lived in 

 the rivers. 



i. Unless, as some have supposed, but which is very improbable, 

 there were no climatic zones in the Palaeozoic, and conditions of tem- 

 perature were equable over the whole globe, related or identical spe- 

 cie$ of eurypterids should be found in deposits geographically situ- 

 ated in a circumpolar zone, not necessarily the same as the climatic 

 zones of the present. 



2. Eurypterid remains should be expected to occur in deposits 

 of limited areal extent marking lake sediments, flood plain deposits, or 

 littoral deposits in the sea at or near the mouths of rivers. 



3. Eurypterids which inhabited the streams of one river system 

 would be more closely related than those living in the tributaries of 

 different and entirely distinct systems, and in general this would mean 

 that forms which lived in the rivers of one continent in any period, 

 would constitute a group of related genera and species, while those 

 living in the rivers of another continent would constitute a distinct 

 group, the individuals of which would be related; and if the different 

 continents should remain unconnected for a long time, geologically, 

 distribution and evolution would continue on each land mass, but we 

 would not expect any of the individuals from one continent to migrate 

 to another, so that succeeding faunas should not show interconti- 

 nental affinities, though phylogenetic relations should be discernable 

 on each continent. It must be remembered, however, that remains 

 of faunas from both continents might be carried into basins which 

 received the simultaneous drainage of rivers from each. 



'The importance of distinguishing between dispersal, the passive and migration, the active 

 distribution of organisms has been insisted upon by Grabau (Principles, p. 1041). 



