RECORDS OF MEETINGS 373 



Medina. The Lower Ludlow is present in the south of Gotland and 

 overlies the beds found in the north. It is perfectly evident if this inter- 

 pretation is correct that the sea withdrew here, and that there was a 

 period of exposure sufficiently long to permit of the removal of the beds, 

 which are now absent in the northern part of Gotland. This is proved 

 by the paleontology of the region, as well as by the physical character of 

 the rocks, especially the sandstone, which is a sandstone of purely conti- 

 nental origin, and was in large part worked by the wind and corresponds 

 to our Salina beds. 



Miss 'Connell stated that in Pre-palseozoic time the Oesel region was 

 composed of crystallines and was worn down to a peneplain. Upon this 

 surface the sea advanced from the south and southeast. This peneplain 

 was not perfect, it being a little irregular and slightly tilted. First 

 came the Cambrian, then the Ordovician, then the Silurian, and at the 

 end of the Silurian period the sea retreated; some of the continental 

 deposits were spread out over the area. Then the region was peneplained. 

 Erosion was caused by rivers flowing in a radial direction, which wore 

 off a deal of the surface. Finally only two islands were left. Dago and 

 Oesel, the rest of the region being submerged. 



The most important fossils found here are eurypterids, which are world 

 famous on account of their almost perfect preservation. Nothing has 

 been changed in the preservation of these animals ; even the hairs on the 

 outer shell are intact. This horizon is only a foot or two m thickness, 

 yet thousands of organisms compose the mass. These eurypterids were 

 carried there by the rivers of that time. It is interesting to note that 

 their nearest relatives are found in western New York, which are the 

 second best preserved fossils in the world. This may be explained by 

 the fact that in Palseozoic time there was a continent extending from 

 North America to western Europe, which was drained by rivers inter- 

 lacing with one another; this enabled the animals to migrate from 

 one river to another. The New York formation is similar to the one of 

 Oesel. There is a thin layer of limestone, which contains eurypterids, 

 followed by a conglomerate of about one foot in thickness, which marks 

 the break between the limestone beds of the lower and upper Ludlow. 



The two latter papers were discussed by Doctors Grabau, Johnson, 

 Knight and Eeeds. 



The Section then adjourned. 



Chester A. Reeds, 



Secretary. 



