STATS GEOLOGIST. 55 



i made from an earthy impalpable powder. 1 have 

 portnnity, however, to submit any samples to tlic 

 ction of a competent lithographer, which alone wonld 

 ■ the value of the rock for this pur] 

 ks lower in the group are seen outcropping successively 

 along tip' the island, from Dickinson's quarry to Pirate 



Haabor, which, tated, is not more than three miles, 



nearly al »ng the strike of the formation, from the first appear- 

 anee of rocks "1" the Hudson River Group. The formation re- 

 appears 00 the northwestern side of the island at Brown's and 

 Seaman's .planus (790 and 796). An experimental quarry 

 of the ship canal company was opened in this vicinity in the 

 part ef the group (792), but v. eqnently aban- 



The same rocks are seen at numerous points as far 

 . neighborhood of the old British Fort, the northern 

 he point of land at the west end of the island 

 being of the Clinton Group. 



Th»' rocks of this group contain few fossils, but among our 



collections I recognize the Avicula, Murchisonia and Cythcrina 



( Leper d ilia? j, referred to by Prof. Hall. The latter, particu- 



at all the localities, and throughout the 



; the formation. At Dickinson's quarry, 



- are seen above the Clinton rocks from 



fOllr to >ix inches thick, somewhat blotched with red, and 



fly ripple-marked The resemblance to the Medina 



thai «-ne expects next moment to find Lmgula 

 'i in it, arch has revealed no Organic 



r,p cuts across the BOOtbern part of St. Joseph's 

 I and passes On in the direction of the southern shore of 

 afunnusco Hay. 



6. — Niagara Group. 



The principal part of the promontory known as Marblehead 

 y of Qrummond's Island, is comp< 



! by the New York geologists, 



