316 The Taconic Question Restated. [April 
Arenaceous Slate group, the rocks of all of which, from the de- 
scriptions, and the specimens which I have been permitted to 
examine, are apparently identical with the Lower Taconic as 
seen in Pennsylvania and elsewhere. This great system, accord- 
ing to Rominger, rests m some parts upon a gneissic and gran- 
itoid series (his Granitic group) and in others upon a great 
Dioritic group, chiefly of massive and schistose greenstones, 
with more or less chloritic varieties, and with closely associated 
serpentines, the whole group having the characters of the typical 
Huronian series. For many of the details respecting these rocks, 
elsewhere given more at length, I am indebted to the courtesy 
of Rominger in permitting me to consult his yet unpublished 
Report of the Geological Survey of Michigan for 1881-1884. 
It appears from a letter by Emmons to Marcou, dated December, 
1860, and published by the latter in 1885, that its author had 
long before “claimed that the Huronian was only the Taconic 
system.” 
It is now evident that two widely distinct and stratigraphically 
discordant series have, around the basin of Lake Superior, been 
confounded under the common name of Huronian. It should, 
however, be said that their distinctness was noted by Logan as 
early as 1847, when he described the lower division (Animikie 
—Lower Taconic) of his Upper Copper-bearing group (its upper 
division being the Keweenian) as resting, on the north shore of 
Lake Superior, unconformably upon the ancient greenstone and 
chloritic group, to which the present writer, in 1855, first gave 
the name of Huronian, and of which fragments are there fourid 
in the basal beds of the Lower Taconic. 
§ 34. Taconic (Lower Taconic) rocks, according to Emmons, 
are found near the Hot Springs of Arkansas, and probably occur 
elsewhere farther west at the base of the paleozoic. Many con- 
cordant observations show the existence of a similar series in 
Cuba, Trinidad, and Venezuela, and also in Brazil, where they 
constitute the Itacolumitic series, already compared by Oscar 
Lieber with that described by him in South Carolina. I have 
called attention to the presence in the Alps of a great series 
lithologically similar to the Lower Taconic, including the so- 
called lustrous schists or sericite schists, with granular marbles, 
anhydrite, quartzites, etc., as well displayed in the Mont Cenis 
tunnel and in the Apuan Alps. These crystalline rocks have 
