210 



jV. II. Darton — Upper Silurian rod's of 



lent to the Oneida-Medina of the New York Survey, but the 

 slate referred to may be that of Ordovician age immediately 

 underlying, or of the slaty rocks of the various formations over- 

 lying the Lower Helderberg. Dr. Horton, however, considered 



Upper Silurian area near Cornwall Station, Orange Co., N. T. : Scale one metre 

 sr-fgmm. Blocked area, limestone; finely blocked, shaly limestone ; dotted, sand- 

 stones and conglomerates ; black, Water-Lime rock ; simply lined, shales. 



the slates of this district as the "Transition " argillite of Prof. 

 Eaton, which is equivalent to the Primal slates of Prof. Eogers 

 or the highest member of Dr. Hunt's Taconian series, which 

 would make it appear possible that he had considered these 

 limestones to be Potsdam or Trenton. In continuation, Dr. 

 Horton states that the characteristic fossil is an " encrinite 

 although many others occur." The associated grit rocks were 

 considered Oneida-Medina, similar to others in the county. 



Prof. Mather in his final Eeport, p. 362, agrees in this last, but 

 states (p. 351) that the limestones belong to the Catskill shaly 

 division and contain Strophomena rugosa and S. radiata in 

 abundance. Dr. Horton's statements are quoted in full. Again, 

 on p. 490, the limestones are referred to, and the opinion of 

 their southward extension considered untenable. On p. 618, 

 the dip is stated. Several sections of the district are given by 

 Mather, one on plate 5 (fig. 13) is stated to be very imperfect 

 in a note on p. 637, and one on plate 45 (fig. 1) is offered in its 

 place. Another section on a larger scale, and of the mine 

 alone, forms fig. 14 on plate 5, but is very incomplete. 



In 1863, G. Dennison, in the Eeport of the New York Agri- 

 cultural Society, notes the occurrence on the remarkable geo- 

 logical map of Orange County accompanying his paper. He 

 also repeats the section by Mather last noted. In 1868, the 

 locality was shown on the useful map accompanying the Geology 

 of New Jersey by Prof. G. H. Cook. In 1878, Dr. T. S. Hunt 

 referred to the locality and quotes Mather and Horton.* 

 * Azoic Rocks, Eeport E, 2d Geological Survey, Pa., p. 36. 



