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 the 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 
series.’? 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 toward 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. 3 Op. cit., opposite p. 52. 
4 Dr. J. 8S. 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 (Gceppert). 
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. 
