prosser.] CONCLUSIONS. 73 
reported, the above, as stated by Prof. White, being common Hamilton 
fossils. 
In reference to the correlation of this horizon with the New York 
Tuily, the professor said: "The Tully limestone is identified in this 
region only by its appearance; its fossils, as may be seen from the list 
above given [the one quoted above], are of the common Hamilton 
forms. If may be merely the upper portion of the Hamilton; but as 
the beds immediately above it are certainly the representatives of the 
New York Genesee, there can be no impropriety in referring the lime- 
stone to the Tully horizon.'' 1 
Eecently Prof. White wrote me as follows: "With reference to the 
identification of the Tully limestone in G 7 ,it was entirely on the strength 
of the stratigraphic order, and not upon the fossils as then stated, so 
that it may well be a portion of the Hamilton." 2 
The exposures referred to the Tully limestone in central Pennsyl- 
vania have not been examined by the writer; but since they contain 
fossils that occur in the typical Tully limestone, are capped by shales 
which are nearly unfossiliferous (not by shales containing an abundant 
fauna of the Upper Hamilton, as in Monroe and Pike counties), it is 
possible that this horizon represents the Tully limestone of New York, 
and in this case, the horizon is not the same stratigraphically as the 
so-called Tully limestone of Monroe and Pike counties. 
Prof. Lesley has considered particularly the Tully limestone in his 
final report, and it is important to review his opinion in reference to the 
Pennsylvania zone referred to this formation. He says: "In eastern 
New York, the Tully is wanting. From the Chenango River eastward 
a hundred miles, to the valley of the Hudson, at Gatskill, no Tully lime- 
stone outcrop can be found between the Genesee and Hamilton forma- 
tions; it was not deposited in this part of the sea; nor has it been seen 
in southern New York as far as the Delaware River; but its outcrop 
begins again in Pike county on the eastern point of Pennsylvania and 
extends westward to the Lehigh River, a distance of GO miles." 3 A 
sketch map is given showing what is called the "Northern outcrop of 
the Tully" across central New York, and the "Southern outcrop of 
Tully limestone " across central and eastern Pennsylvania between the 
Susquehanna and Delaware Rivers. 4 It is further stated that between 
the north and the wegt branches of the Susquehanna River " the forma- 
tion is at its thickest (00 feet), and its lithologic character the same as 
in New York. But, on the other hand, all its fossils are of Hamilton 
type, not a single peculiar New York Tully species having been as yet 
observed in it. On the Delaware it is nowhere more than 30 feet thick, 
retains its character, but holds no special Tully shells. The impor- 
tance of these facts in their bearing upon our views of Paleozoic depo- 
» Ibid., p. 76. 
2 Letter of Prof. White, January 19. 1892. 
■^Sum. Desc. Geol. Peim., Vol. II. ]>. 1313. 
"Ibid., p. 1314. 
