WILLIAM B. DWIGHT. Plat 
ledges, as before, proved unfossiliferous; but as we 
struck away from the farm-road into the woods to the 
north, Mr. Walcott soon found loose fragments of less 
compact, ferruginious, decomposing, quartzose rock, 
completely filled with organic remains ; among these 
could be detected glabellasandspines of Olenellus, with 
a species of brachiopod, and other fossils. In a few 
minutes we succeeded in finding this fossiliferous rock 
in place, showing, in great abundance, its fossils which 
had mostly been injured by the oxidation of iron, Mr. 
Walcott soon returned to the ledges of the limestone 
which immediately overlies the quartzyte, where it was 
exposed in the farm-road, and by discovering there 
opercula of Hyolithellus micans, thus proved that it 
belongs to the same horizon as the quartzose strata. 
These fossils were also found in the little limestone 
quarry above mentioned. 
Thus the question of the geological age of the quartzyte 
of Stissing mountain, as also that at the base of Fishkill 
mountain, (which we visited together immediately after 
leaving Stissing,) after years of uncertain speculation, 
has been solved ; and its solution covers also the kKnowl- 
edge of the age of the immediately overlying limestone. 
The credit of these discoveries belongs chiefly to Mr. 
Walcott, whose long and intimate acquaintance with the 
pre-Potsdam strata, was of great service in the search. 
The fossils discovered have been identified by Mr. 
Walcott, so far as the present imperfect specimens will 
permit, as follows: 
From the quartzyte:—Olenellus asaphoides, or 
Thomsoni ; probably the former; glabellas and cheek 
spines ; brachiopods, probably Zvriplesia, and Oboled/a, 
Species not determined. From the limestone immedi- 
ately overlying the quartzyte:—Hyolithellus micans ; 
opercula very well defined, rather abundant. Odolella, 
Sp. 4 
95 
