BUFFALO SOCIETY OF NATURAL SCIENCES 1 5 



period and the evolution of distinctive characters .... had 

 progressed to so sharp a differentiation that we are compelled to carry 

 back farther in history, some of the commoner generic designations. 

 These remains in the Frankfort [Schenectady] shale are distributed 

 through fully 1500 feet of strata off a northeast-southwest coast line 

 in an area of maximum deposition." Clarke and Ruedemann have 

 described eleven species 3 Eurypterus megalops , E. pristinus , E. ? (Doli- 

 chopterus ?) stellatus, Eusarcus triangulatus , E ? longiceps, Dolichop- 

 terus frankfortensis, D. latifrons, Hughmilleria magna, Pterygotus 

 nasutus, P. prolifica, Stylonurus ? limbatus. 



A few fragments found as early as 1874 in the upper part of the 

 Cincinnati group near Clarkesville, Clinton County, Ohio, were origi- 

 nally described by S. A. Miller (174) as Megalograptus welchi, under 

 the mistaken supposition that they represented a graptolite, but were 

 later determined by A. F. Foerste to be eurypterid remains. The 

 specimens are .much broken, representing two endognathites with 

 one postabdominal segment. They occur in a blue marl three feet 

 above a wave-marked layer of limestone, in the Liberty beds where 

 they are associated with a typical marine fauna mainly of crinoids 

 and some trilobites. 



Siluric. Lower Siluric or Niagaran. In the Lower Siluric are 

 several cases of the presence of eurypterid remains in marine forma- 

 tions. Hall's species of Eurypterus prominens from the Clinton green- 

 ish sandstone of Cayuga County, New York, was described from a 

 single cephalon, and an unidentified species of Eurypterus is recorded 

 from the Arisaig of Nova Scotia (39, 87). Whiteave's Eurypterus 

 (Tylopterus) boylei from the Guelph dolomites of Ontario is a species 

 founded upon a single somewhat crushed, but otherwise nearly com- 

 plete individual. It is found in a porous, coarse-grained dolomite, 

 and shows an unusually thickened exoskeleton, a thickening common 

 in other members of the Guelph fauna and indicating, according to 

 Clarke and Ruedemann, extremely saline conditions (39, 218). 



Quite recently a new eurypterid horizon has been discovered by 

 M. Y. Williams in the shales overlying the Lockport and underlying 

 the Guelph of Ontario, Canada. Along the banks of the Eramosa 

 River between Rockwood and Guelph the top of the Lockport forma- 

 tion is exposed, and is seen to consist of a series of " thin-bedded, dark 



3 Eurypterus ruedemanni. This name is proposed for the species called by Clarke and Ruede- 

 mann E. megalops, that name having been previously occupied by Salter (1859). The fact that 

 Woodward referred Salter's species to Stylonurus does not restore the validity of the name megalops 

 for Eurypterus. 



