THE EURYPTERIDA OF NEW YORK 99 
the Lower Siluric eurypterids thus far known were hence still purely 
marine.' 
| The rich faunas of the Kokomo and Salina beds (the latter containing 
these creatures by thousands) are all intercalated in distinctly marine de- 
posits; the Kokomo beds carry such brachiopods as Conchidium 
colletti and Wilsonia kokomoensis, and the Salina euryp- 
terid shales Leperditias, Pterineas (P. subplana), cephalopods (Or- 
thoceras, Gomphoceras), marine gastropods, Conularias, Lingulas and 
Orbiculoideas. The same is true of the European eurypterid horizons 
intercalated in the Wenlock and Ludlow beds of Great Britain, and of 
the Oesel beds of Russia. ~The latter horizon lies between the lower 
-Oesel zone with heavy coral banks, numerous trilobites (as Calym- 
mene blumenbachi, Encrinurus punctatus, etc.) and 
1 The investigation of this Frankfort shale fauna proves it to be restricted geo- 
graphically to the exposures of the formation in the lower Mohawk valley, where it 
seems to pass with equal profusion through a thickness of several thousand feet. Speci- 
mens have been obtained in the Dettbarn quarry at Schenectady, the bluestone quarries 
at Aqueduct and Rexford Flats, on both sides of the Mohawk river; and a profuse 
association of Sphenothallus and the eurypterids was found in the upper part of the 
section described by Cumings [N. Y. State Mus. Bul. 34, p. 451] from Rotterdam Junc- 
tion, west of Schenectady. In much higher beds of the Frankfort shale the same fauna 
was obtained in abundance at quarries at Duanesburg and Delanson, on the Schenec- 
tady branch of the Delaware & Hudson Railroad, and still farther southwest in the 
reéntrant of the Helderberg escarpment, caused by the Schoharie creek, in exposures 
along that creek above Schoharie Junction. In a ravine of a small stream which joins 
the Cobleskill between Central Bridge and Howes Cave (mentioned by Grabau [N. Y. 
State Mus. Bul. 92, p. 102] on account of its fine exposure of the Brayman shale), the 
curypterid fauna could be traced quite up to the Brayman shale. Thus in the western 
part of its range it occupies the whole thickness of the Frankfort shale, unless it is absent 
in the lowermost part of the formation, not yet found in good exposures in that region. 
The fauna does not seem to extend to the western localities, for it has not been observed 
in the Frankfort shale sections at Frankfort and Ilion, where the fossils have been 
very thoroughly studied by the junior author. 
Toward the southeast the last traces of the eurypterids are found in the sandy 
shales exposed along the Vly, below Voorheesville. Here the eurypterid beds are fol- 
