34 S. W. Ford—Primordial Rocks of Troy, N. Y. 
quarter. In reply Mr. B. informed me that he was just then en- — 
aged upon a collection of new fossils from the Lower Potsdam ~ 
riauon below Quebec, which he strongly suspected to be — 
identical with my own; and on comparison it was found that 
fifteen out of the eighteen species from Troy were held by usin ~ 
common, and shown to be perfectly identical. Such an un- — 
looked for result of course surprised us greatly. That the Lower — 
Potsdam formation below Quebec, and the western portion o 
the Taconic series near hee are of the same age, there seems 
now but little room for 
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its ala of lateral muscular impressions and two sm er, dor- 
diating from a point near one side;” the other as “larger, 
i The former occurs quite 
Sie aa a in the Troy limestones, and is a very beautiful little © 
object. It varies in size from a mere point to a diameter of © 
three lines. Perfect specimens have a rich, polished appear- | 
ance. The other occurs more rarely. As might naturally be 
expected, these rocks contain immense numbers of Hyolithes. 
Indeed, large —— of the limestone are often almost wholly 
composed of them. 
ithout scant this formation in New York will yet afford — 
_ new species. ‘The even-bedded limestones east of Troy, . 
to which especial attention has been given, as well as portions — 
of the Oe ent are literally loaded with fossils, and 
Sabi hly to repay idee ye for a long time to come. — 
heir associated slates, shales and sandstones lave as yet af 
forded no fossils. Near Tats ee, however, where what is 
at present regarded as a lower member of the formation, con-_ 
sisting of heavy and thin-bedded Bray sandstones with inter- 
stratified black slates, is exposed, a few obscure Fucoids have 
been found, but these rocks have been but imperfectly investi- 
ted. Neither the thickness nor precise eastern limit of this _ 
ormation has yet been ascertained. 
Troy, N. Y., May 24, 1871. 
* These rocks have hitherto been referred, though with some doubt, to the Cale z 
ciferous portion of the Quebec Group; but all modern investigations in our olde 
strata have steadily A gate to their higher antiquity; and it is simply justice t0 
state that, by several geologists besides those who have adopted Prof. Emmons’ 
views of their age, this has long been suspected. 
