FORMATIONS OF SILURIAN AGE. 55 
soft, red, arenaceous, more or less shaley, unfossiliferous beds, and in 
both regions the first fossil fauna, which appears in higher beds lying 
in a perfectly conformable series with the conglomerate beds, is 
identical. . 
The western side of the Green Pond paleozoic area is cut off by pro- 
found faults along its entire extent, and it is altogether probable that. 
at the time of its deposition, the Green Pond conglomerate was con- 
tinuous with the Shawangunk conglomerate of the Kittatinny moun- 
tain, and that it has been removed by erosion from the intervening 
Highlands and the Kittatinny valley. 
MEDINA—LONGWOOD SANDSTONE. 
In the Delaware valley this formation covers a large portion of the 
northwestern slope of the Kittatinny mountain, and doubtless occupies 
the greater portion of the valley lying west of the Wallpack ridge, 
although the surface rock is deeply drift-covered in the valley. The 
formation is a soft sandstone, which is often somewhat shaley and 
has a deep red color. It is absolutely barren of organic remains. 
It is impossible to determine its thickness accurately, owing to the 
indefiniteness in the field of its upper limits and numerous low folds 
and small faults which affect it. At the Delaware Water Gap 1,645 
feet is given by the Pennsylvania Survey* as the thickness of the 
beds which we class as Medina, with 740 feet additional not exposed, 
but probably belonging here—a total of 2,585 feet. An estimate by 
Dr. Kiimmel, based on its dip and width of outcrop near Poxino 
island, gave 2,305 feet. 
This formation has always been referred to the Medina sandstone 
of the New York series, and although it cannot be considered as‘ being 
strictly equivalent to the typical Medina of Western New York, the 
name may be retained for the present or until the relationship between 
this formation in the Appalachian province with that in the interior 
is better understood. 
In the Green Pond mountain region Darton has called the forma- 
tion overlying the Green Pond conglomerate, which is exactly similar 
to the upper part of the Medina of the Delaware valley in its lthologic 
* Second Penn. Geol. Surv., Rep. G. 6, p. 340. 
+ Bull. Geol. Soc. Am., vol. V., p. 382 (1894). 
