68 The Tacontc — Marcou. 
the rules of stratigraphy, Hthology and palaeontology and in direct 
opposition to his statements, that he "takes up the question of the 
Taconic system in geology, as one that can only be intelligently 
understood and decided by the application of the principles." \^Loc. 
cit. p. 230]. The only fossil of any value, as truly characteristic 
of the typical Potsdam, the Conocephalites minutus of Keeseville 
has not been found anywhere in the whole original Taconic 
area notwithstanding its great proximity to Keeseville. As to the 
two Lingiilepses^ every geologist and palaeontologist knows 
how that genus is unreliable, passing through several zones 
without any perceptible changes in the species. 
The fossils found in Dutchess county, and at some other 
points, show that lenticular masses of limestone inclosed in the 
Taconic slates contain primordial fossils, and that they belong 
very likely to the lower part of the Phillipsburgh and Pointe 
Levis group. 
Mr. Walcott believes that the only group of strata existing 
between the Georgia slates and the Calciferous sandstone, is 
the Potsdam; a theoretical view which suppresses four-fifths of 
the upper Taconic and of the supra-primordial fauna. We have 
there the explanation of his constant effort to bring out a Pots- 
dam formation first at Georgia and then in the original Taconic 
area. It is a misdirected effort. A careful revision and good 
descriptions of all the fossils existing in the typical Potsdam of 
the western part of lakeChamplain extending from Port Henry, 
Keeseville, Potsdam and Chateaugay, are much wanted and a 
great desideratum. For the name "Potsdam sandstone" or 
"Potsdam formation" has been used so freely during the last 
forty years, that it is almost certain that nine-tenths of what has 
been referred to it, does not belong to the Potsdam, even with 
the help of "off-shore deposits." Mr. Walcott disagrees here 
also with his associates, for the other adversaries of the Taconic 
have regarded all the strata united under his number 2 as be- 
longing to the Champlain system. 
No. 3 or "limestone and marble belt" (Stockbridge limestone) 
is regarded by Mr. Walcott as the equivalent of the Trenton, 
Chazy and Calciferous or Calciferous-Chazy-Trenton (C. C. 
T.) of the Champlain valley. No list of fossils is given; no 
ithickness, referring for the proof of the age of that group, to 
