RAYMOND: CORRELATION OF THE ORDOVICIAN STRATA. 251 
Valley, in all of which places it occupies a thin formation, its vertical 
range never exceeding forty feet. A very few specimens have been 
found in the lowest layers at Trenton Falls, but it is absent from more 
northern outcrops of the Trenton. It is not found in the Trenton 
anywhere in the region of New York west of the Adirondacks, it is 
absent from the Trenton of Ontario and Quebec west of Montreal, 
and it is absent from Minnesota. The second occurrence in New 
York is not in the Trenton, but in the typical Utica, at Rome and the 
, 
; vicinity. It occurs also in the Frankfort, and still higher, in the 
Pulaski. 
‘ In the vicinity of Quebec the second appearance of Cryptolithus is 
. in the light-colored sandy shale about 400 feet above the top of the 
limestone of the Trenton, and above the dark “ Utica”’ shale. 
At Bellefonte, Penn., the earliest appearance of Cryptolithus tessel- 
latus is, as in New York, just above the limestone containing the 
Leray fauna, and it reappear’ in the upper fifty feet of the 600 foot 
Trenton section, at the point where the limestone begins to pass over 
into shale, and just before the first appearance of Triarthrus beck. 
In Kentucky, Cryptolithus appears first in the Logana (Hermitage), 
only a few feet above the base of the Trenton, and does not reappear 
till the Cynthiana, just at the top of the Trenton or base of the Eden. 
On the Ohio River at Cincinnati it is in the Cynthiana, and the Lower 
Eden, and appears again in the Maysville. 
The occurrences are so exceedingly alike, and there is so great an 
indifference displayed as to the character of the sediments, that I am 
inclined to look upon Cryptolithus as an exceedingly good horizon 
marker. If this be the case, then the Schenectady formation is to be 
correlated with the Utica, and, probably, the Frankfort. 
Se ee ee 
CORRELATION OF THE TRENTON IN AMERICA. 
One great obstacle to any correlation of the kind attempted in 
this study is the fact that we have as yet reached no satisfactory 
solution to the problems presented by our American Ordovician strata. 
By far the best correlation tables for the Ordovician are those recently 
presented by Drs. Ulrich and Bassler. My own differs radically from 
theirs, and I am therefore compelled to traverse the principal outlines 
of the subject in justification of the departures which I have made 
from former schemes. 
