BUFFALO SOCIETY OF NATURAL SCIENCES 233 



cestor of the Bertie forms. Not only this; it actually came from the 

 same region as the later types. For it must be apparent that the 

 rivers of Atlantica, which furnished the deposits of the Bertie, were 

 also in existence during Pittsford time and must have mouthed into 

 whatever remnant there was of the Niagaran sea. It is not particu- 

 larly likely that the ancestors, if so we may call them, of the Upper 

 Siluric rivers occupied precisely the same location as the Bertie or 

 Herkimer rivers, but undoubtedly they existed in somewhat the same 

 general region. Therefore, what is more likely than that during 

 Pittsford time these southward-flowing rivers from the continent of 

 Atlantica should bring down the remains of organisms living in them? 

 These rivers could not themselves have supplied the muds of the 

 Pittsford shales, for they came from a limestone region, and whatever 

 sediments they carried must have been of the nature of waterlimes. 

 If such calcareous deposits were spread out on the flood plains of those 

 rivers they are now no longer visible, for subsequent erosion has 

 removed all traces of deposits of Pittsford age in Canada; but there 

 is where a eurypterid fauna would be expected to occur, just as in 

 Bertie time when waterlimes were deposited farther south the fine 

 eurypterid fauna is found. This explanation makes it entirely clear 

 why E. pittsfordensis is related to no form yet known from the Sha wan- 

 gunk, but has characteristics showing that it was ancestral to forms 

 in the Bertie. New discoveries have corroborated this theory. 



Professor C. J. Sarle has discovered the Pittsford fauna at a new 

 locality in New York State. The details of this have not yet been 

 published, but it is known that both Eurypterus pittsfordensis and 

 Hughmilleria are common. The rock is a gray shale and the material 

 was undoubtedly supplied by the rivers of Appalachia. Since Hugh- 

 milleria is otherwise known only from deposits derived from Appala- 

 chia it is reasonable to assume that the same rivers which carried 

 in the muds also brought in the Hughmilleria. The abundance of 

 E. pittsfordensis is not surprising, for if the rivers from Atlantica 

 emptied into the Pittsford basin there is no reason why they should 

 not bring as abundant a fauna as did those from Appalachia. If, 

 as is to be expected, the basin in which these deposits were laid down 

 was at times a fresh water lake, the eurypterid faunas of both river 

 systems may have met and lived for a time in this water body. They 

 were then killed by the sudden incursion of the Guelph sea which 

 brought with it the remnant of the Guelph fauna found in the inter- 

 calated limestone. 



