NEW YORK STATE MUSEUM 



of the whorl; Belle rophon patulus [fig. 176], charac- 

 terized by a broadly-flaring, nearly circular aperture and a faint 

 median deflection of the lines of growth. 



The trilobites are represented by Homalonotus d e k a y i 

 [fig. 177], a large elongate, linguiform species, with faintly marked 

 pygidium, rectangular glabella, subtriangular cephalon, and 

 thorax scarcely trilobate; P li a cops r a n a [fig. 178], charac- 

 terized by the broad subpentagonal, strongly pustulose glabella, 

 prominent eyes, and nearly semicircular pygidium. 



The problematical marking, Spirophyton velum [fig. 

 179], which differs from the species in the Esopus chiefly by its 

 smaller size, is also common in the sandy layers of the Hamilton. 



Sherburne formation 



The Hamilton sandstones grade upward into a series of bluish 

 sandstones and greenish shales which constitute the Sherburne 

 formation of Vanuxem. West of Schoharie county, from the 

 Chenango valley to the meridian of Cayuga lake, where this for- 

 mation passes horizontally into the Naples shales of the Portage, 

 it is separated from the Hamilton beds by the Tally limestone 

 and the Genesee shales. In eastern New York these formations 

 are absent as lithic units, and the Sherburne directly succeeds 

 the Hamilton. Its thickness is 250 feet or over, and its fossils 

 when not merely plant remains, constitute together with those 

 of the succeeding Ithaca beds a modified Hamilton fauna, which 

 gradually disappears westward. In Greene and Ulster counties, 

 this formal ion is unfossiliferous with the exception of scattered 

 planl remains and probably includes the horizon of the "North 

 river bluestone." 



The mosl accessible locality for the examination of this rock is 

 in the upper slopes of Moheganter hill as described in the sections 

 in chapter 5. 



In the Schoharie river valley region the line of separation 

 between (lie Hamilton and Sherburne formations is not as clearly 

 shown for part of the distance as it generally is farther west. 

 This is due largely to the heavy mantle of drift covering the 



