BUFFALO SOCIETY OF NATURAL SCIENCES 247 



break or period of emergence has recently been recognized by Grabau 

 as affecting all countries bordering on the North Atlantic and has 

 been recorded for North America, Scotland, Oesel (by the author), 

 and even in what was formerly supposed to be the continuous section 

 in England (89b). There was a widespread diastrophic movement 

 at the end of the Niagaran marking a broad expansion of continental 

 areas during Salina time so that perhaps nowhere are there preserved 

 to us the marine sediments of that period. Certainly the North 

 American eurypterids were cut off from marine routes of migration 

 with which most authors like to provide them, and yet migration 

 seems to have gone on. The Salina in North America was a period 

 of aridity west of the mountain mass of Appalachia, but that chain 

 died out northward and probably merged into the continent of 

 Atlantica, there being no northeast Atlantic sea-lobe at that time. 

 Several possible lines of fluviatile migration were open and nothing is 

 more probable than that emigrants from Appalachian north and 

 northeast flowing rivers should have entered some one of the tribu- 

 taries of the systems on Atlantica. The exact mode of transit can 

 not be determined, but many routes were open. Indeed, it is pos- 

 sible that migration occurred even in Pittsford time from the rivers 

 of Appalachia into one of the Pre-Bertie rivers which we have seen 

 probably existed in the western New York region even during the 

 Niagaran (p. 113 above). This much we may conclude: There were 

 many routes and possibilities of migration open to eurypterids 

 living in the rivers of Appalachia during the Lower and Middle 

 Siluric, but continuous marine paths to Europe were non-existent. 

 Furthermore, the distinctness of the Ludlow fauna as a whole from 

 any of the faunas of Appalachia, but the close relationship of one 

 species from the former to two from the latter is inexplicable for 

 members of a marine fauna, but normal and expectable for members 

 of fluviatile faunas. 



The Old Red Sandstone Fauna. The last of the European forma- 

 tions which is believed to have been derived from the continent of 

 Atlantica is the Old Red sandstone. Most the eurypterids occur in 

 the beds in various localities in Forfarshire. By far the most abun- 

 dant species is Pterygotus anglicus which finds it nearest relatives in 

 Pterygotus bufaloensis and P. monophthalmus from the Bertie, and 

 P. osiliensis from the Baltic region. The various points of similarity 

 are so well known that it is not necessary to take them up. Ptery- 

 gotus minor is a small form found associated with P. anglicus, but it 



