BUFFALO SOCIETY OF NATURAL SCIENCES 105 



by the Niagaran limestones which would furnish pure clastic lime- 

 stones and not impure siliceous muds. The only area from which 

 the muds could be derived, was the land to the east. That the black 

 mud was merely an extension of the muds forming at intervals on the 

 Shawangunk delta must be obvious when it is seen that in that direc- 

 tion was the only source of the muds and that the Shawangunk 

 muds contain the same eurypterid fauna. This will be more fully 

 discussed in Chapter V. 



The areal distribution of the Pittsford is limited. The shale is 

 known from Monroe county and from Oneida county, New York. 

 Both eastward and westward it dies out, the Vernon red shale rest- 

 ing directly upon the Niagaran. In a few localities black shales have 

 been found which have been correlated with the Pittsford, but they 

 contain no eurypterids. Such is the black shale at Buffalo, on Grand 

 Island, and the dark shale in Herkimer county above the Lockport 

 dolomite which contains no fauna except a few Lingulas. The out- 

 crop in Oneida county is at Oriskany creek, where in a bluff occur 

 some dark gray shales, about 21 feet below the base of the Vernon 

 red shale, with intercalated waterlimes and dolomite beds. These 

 dolomites contain fragments of one species, Eusarcus vaningeni, to- 

 gether with lingulas and orbiculoideas. Both the areal and vertical 

 distribution, then, are limited, in much the same way as in the Bertie, 

 and the source of this calcareous material may likewise be the same. 

 (See beyond, p. 234.) 



If the eurypterids of the Pittsford shale were brought in by the 

 rivers coming from Appalachia, the waters in the region of deposition 

 would become freshened by the inpouring of the river waters, and 

 marine forms would thus be kept out. It is often assumed that the 

 Pittsford shale marks a periodic increase in the salinity of the water, 

 but in that case we are faced by a double problem: if the muds were 

 not deposited by rivers, where did they come from, since they could 

 not have originated in the sea? and then again, the question arises, 

 where did the eurypterids suddenly come from? The muds might 

 be aeolian, but not the eurypterids. The only possible conclusion 

 seems to be that the eurypterids and the black muds both were 

 brought by rivers from the land, i.e., that the eurypterids were river- 

 living organisms. 



In this connection attention may be called to the fact that the 

 species of eurypterids in the Pittsford and Shawangunk and to some 

 extent the genera as well, are entirely different from those of the 

 Bertie. This is not alone accounted for by difference in age, but is 



