FORMATIONS OF SILURIAN AGE. 6H 
POXINO ISLAND SHALE. 
The summit of the Medina formation in New Jersey has not beer 
observed, but the lowest formation above that sandstone and having: 
outcrops in the State is a buff or greenish, calcareous shale, irregularly 
bedded, in layers one inch or less in thickness. In the bottom of 
the Nearpass section about one foot of this rock is exposed in an 
excavation which has been made in the talus slope at the foot of the 
bluff. South of Hainesville is another exposure, where a quantity of 
the material has been excavated for road-making purposes. Other 
exposures occur at several points south of Wallpack Centre, but no- 
where have fossils of any description been observed. 
This formation was first described by I. C White,* from Pennsyl- 
vania, in the southwestern extension of the Wallpack ridge, but he 
observed no outcrops in New Jersey. The base of the formation has 
not been observed in New Jersey, but in Pennsylvania it is described 
by White as resting upon a thin limestone formation, which, in turn, 
rests upon the Medina. It is said to be at least 200 feet in thickness 
in Pennsylvania, but only a small fraction of this thickness is ex- 
posed anywhere in New Jersey. 
BOSSARDVILLE LIMESTONE. 
Lying above the Poxino Island shales is a fine-grained, compact,. 
bluish-gray, banded limestone. It is expoged in the Nearpass section, 
in the excavation already mentioned, where its entire thickness 1s- 
twelve feet four inches. From this point south to Peter’s Valley but 
few outcrops are to be seen, but between Peter’s Valley and Flat- 
brookville there are many excellent exposures. The thickness of the 
formation is greatly increased to the south, and although no exact 
measurements could be made, it is at least 100 feet thick below Wall- 
pack Centre. This formation is without question a northward exten- 
sion of the limestone in Pennsylvania, designated by White+ as the 
Bossardville limestone. It is, also, the formation which was called 
the “Ribbon lhmestone” by Professor Cook,t and which was errone- 
* Second Geol. Surv. Penn., Rep. G. 6, p. 145. 
} Loe. cit., p. 141. 
t Geol. of N. J., p. 156 (1868). 
