1892.] NEW YORK ACADEMY OF SCIENCES. 135 



A " section from Woodcock Hill, southeast and east across Skun- 

 nemunk Mountain," is given,' in which it is shown that the struc- 

 ture of the mountain is that of a synclinal fold. Professor Smock 

 says: "The synclinal structure of tl^e Skunnemunk elevation has 

 been shown in the profile, on page 46. The well-defined and normal 

 type of a synclinal fold in this mountain, the order of superposition 

 in the strata of shale, sandstone, and conglomerate, and the numer- 

 ous and almost unbroken succession of outcrops from its base to 

 crest line, make it typical of the whole range of Green-Pond moun- 

 tain rocks. And its relations to the adjacent formations and its 

 fossil organic remains give the clew to the geological age of the 

 serie^.'"^ A sketch map, showing the geological formations near 

 Monroe, is given, the legend of which is " sandstone and conglom- 

 erate of Skunnemunk Mountain (Devonian) ;"* while the geo- 

 logical age is explained at some length in the text, the correlation 

 being determined by means of fossil plants. The Professor says 

 "the Skunnemunk Mountain range appears to afford satisfactory 

 proofs and to give data upon which to base the age of these rocks. 

 The section on page 46 shows a cross-vertical profile of the moun- 

 tain from near Washingtonville to Mountainville, on a south and 

 east line. The section exhibits the gneissic rocks on each side ; 

 the blue, magnesian limestone, the black (Hudson River) slate, 

 and the (Oneida) conglomerate on the west, all having their beds 

 dipping tow^ard the southeast. The slaty sandstones and the thin- 

 bedded grits, or gray sandstones (flagging-stones), are shown, with 

 their inward dips, capped by the peculiar and characteristic red 

 conglomerate. Here the conglomerate and the sandstone are seen 

 above the Silurian slates and limestones. And the former have 

 been preserved in this gently-folded synclinal. Elsewhere it must 

 have been broken up in the uplifting and bending of the strata and 

 afterward removed by glacial forces, which have left so many traces 

 of their planing and polishing work on these hard rocks. 



The occurrence of plant remains in this series has been referred 

 to above. They are found in the gray-red, shaly sandstone of 

 Skunnemunk Mountain. The locality where they can be most 

 readily seen is at the Davison quarry, at the southwest point of the 

 mountain and three miles northwest of Monroe.* A few frag- 

 mentary specimens have been found on the east side, also, and near 

 Woodbury Falls. ^ These plant remains are identified as specifically 

 the same with those collected and described by Professor James 

 Hall, State Geologist of New York, and by Dr. Dawson, of Mon- 



1 Op. cit., fig. 7, on p. 46. 



2 Op cit,, p. 51. ' Op. cit., opposite p. 52. 



* Dr. J. S. Newberry, of Columbia College, N. Y., has identified the follow- 

 ing species in a collection from this locality, now in the cabinet of Professor 

 D. S. Martin, New York City : Lepidodendron Gaspianum (Dawson) ; Psilophyton 

 princeps (Dawson) ; Calamites transitionis (Goeppert). 



5 In a collection of plant remains made in the autumn from these localities, 

 rhizomes of the Psilophyton abound. A species of Calamites also appears. 



