TACONIC QUESTION IN GEOLOGY. 251 
talline rocks. This series is overlaid by what he called the Tonto group, which the late 
studies of Walcott have shown to be Cambrian, and to rest unconformably upon the 
uncrystalline rocks below. As the result of an exploration undertaken for the purpose of 
fixing the relations of these various rocks, it is announced that the Tonto belongs to the 
base of the overlying paleozoic series, and that Powell has established “ the pre-Cambrian 
age of the Grand Canon group.” * Later explorations have shown the presence, in these 
pre-Cambrian rocks, of organic forms compared to Stromatopora. These rocks apparently 
hold the place of the Lower Taconic series. 
$92. Considering the pre-Cambrian age of the Lower Taconic of Emmons to be estab- 
lished, as well as its distinctness, alike from the older crystalline rocks below and from 
the Cambrian series above, to which Emmons had given the name of Upper Taconic—it 
was proposed, by the writer in 1878, to restrict the term of Taconic, for which the alter- 
native name of Taconian was then suggested, to the Lower Taconic of Emmons. + 
The question as to whether the Cambrian is to be regarded as the base of the 
paleozoic series ; or in other words, whether the Taconian should be considered as belonging 
to eozoic or paleozoic time, was discussed by the author, in 1876; when he wrote as 
follows: “It will be found as difficult to draw the line between the eozoic and paleozoic, 
as it is to define that between the mesozoic and paleozoic on the one hand, or between the 
mesozoic and cenozoic on the other. There are no hard-and-fast lines in nature; breaks 
are local, and there is nowhere an apparent hiatus in the geological succession which is 
not somewhere filled.” Referring to the Lingula found by Prime in the Auroral limestone 
of Pennsylvania, it was said ;—‘“this seemingly imperishable type of brachiopods may 
serve, like the rhizopods, represented by Eozoon, as a connecting link between eozoic and 
paleozoic time.” # 
Subsequently, in a paper read before the National Academy of Nciences in April, 1880, § 
it was said of the Taconian series :—‘“ These older rocks are not without traces of organic 
life, having yielded in the Appalachian valley the original Scolithus, and related markings, 
besides obscure brachiopods; and in Ontario, besides similar Scolithus-like markings, 
a form apparently identical with the Eozoon of the more ancient gneisses. We may hope 
to find in the Taconian series a fauna which shall help to fill the wide interval that now 
divides that of the eozoic rocks from the Cambrian. || We should seek in the study of 

* Science, March 16, 1883, page 183. 
ÿ On the Geology of the Eozoic Rocks of North America; Proc. Bost. Soc. Nat. Hist., xix., 278; and Azoic 
Rocks, p. 207. | 
Ÿ Proc. Amer. Assoc. Ady. Science, 1876, pp. 207-208 ; also, Azoic Rocks, p. 211. 
& Canadian Naturalist for 1880, vol. ix, p. 430. 
|| The Keweenian or copper-bearing rocks of Lake Superior, afford apparent traces of life. I quote the 
following from my report in 1878, on Azoie Rocks, p. 237. “There are certain markings in the Keweenian which 
are probably of organic origin. Logan, in 1847, described the occurrence in some of the earthy or so-called 
tufaceous beds of the series, of numerous slender vertical tubes, filled with calcite, haying a diameter of about a 
quarter of an inch, and a length, in some cases, of from eight to twelve inches. Two or more of these tubes were 
often found to coalesce in ascending, and they were supposed by Logan to have been formed by currents of gas 
rising through a pasty mass (Geol. of Canada, p. 71). From’ the observations of the writer, in 1872, on Michi- 
picoten Island, where similar markings were found in an argillaceous stratum, he was led to compare them with 
some forms of so-called Scolithus, and to regard them as due to the burrowing ofannelids. These were accompanied 
by large numbers of two curious forms, the one club-shaped, and the other hemispherical or dome-shaped; each 
