214 THE HABITAT OF THE EURYPTERIDA 



have lived in or along the shore of a shallow, epicontinental sea hav- 

 ing a connection with the Atlantic or other waters to the east. In 

 this restricted sea terrigenous deposits were formed, well represented 

 by the Shawangunk delta. In the pools along shore, where, on ac- 

 count of the more sheltered conditions, only muds were accumulat- 

 ing, the young eurypterids lived. The larvae were hatched in these 

 pools and the early stages in the ontogeny were passed through, then 

 the mature individuals sought the deeper littoral waters. Thus do 

 Clarke and Ruedemann explain the presence of the abundant fauna 

 composed almost entirely of young individuals in the Shawangunk 

 shales at Otisville, New York, and, during the same period, the closely 

 related but mature individuals in the Pittsford shales at Pittsford, 

 New York. 



A comparison, species by species of the forms from the Pittsford 

 and Shawangunk will be given below (p. 225), and it will be seen to 

 show that the two faunas are very closely related, indeed, almost iden- 

 tical except in the size of their individuals, and in the presence, 

 in the Pittsford, of a species of Eurypterus related to a Bertie 

 form to be considered presently. Such similarity might, if taken 

 alone, seem to substantiate the "lagoon" theory. But it is usually 

 impossible to draw very accurate or very far-reaching conclusions 

 from the consideration of faunas or of deposits in a single circum- 

 scribed area or at a single horizon; one must take into account the 

 palaeogeographic conditions in neighboring regions and finally through- 

 out the whole continent if not, indeed, the whole world, and one must 

 consider the source of supply of sediments, the possibilities of migra- 

 tions of faunas and the absolute necessity of a fauna to have a medium 

 in which it can live from one period to another, unless we wish to re- 

 vert to the belief in special creations. Thus, bearing these things in 

 mind, we must account for the origin of the sediments of the Pittsford 

 and Shawangunk and of the succeeding formations, the various water- 

 limes, which contain eurypterids. It has been demonstrated on pp. 

 ioc-6. that the conglomerates and shales of the Shawargunk and the 

 shales of the Pittsford must have come from Appalachia, carried 

 northwards by various rivers. 



Now, assuming for the sake of argument that the succession of 

 events during Salina time was that outlined above (p. 212) then the 

 following conditions are implied: (1) The Pittsford and Shawangunk 

 faunas must have constituted the ancestral stock for the Bertie fauna 

 of Erie and Herkimer counties. (2) Throughout the long period from 



