UPPER PALEOZOIC (deVONIC). 245 
tinct, but there can be no reason whatever for dividing the 
Genesee from tlie Portage, for in the typical section recurrences 
of the Genesee lithological conditions occur up to the very base 
of the Portage sandstones which terminate the Portage group of 
the New York system. 
If, therefore, we follow precedent and speak of a distinction 
between middle and upper Devonian, the Genesee shale certainly, 
and the Tully limestone, so far as its typical fauna is concerned, 
belong strictly to the upper Devonian and not to the middle ; and 
in order to adapt our usage to the accepted usage of European 
standards, when speaking of upper and middle Devonian, we 
should include in the upper Devonian the Genesee shale and so 
much of the Tully as contains the Rhynchonella venustula fauna. 
It is to be noted in this comparison with the European expres- 
sion of the Devonian, that the same general difference observed 
in comparing the eastern continental with the central area of 
America is observed in comparing the area of northern Europe 
with that in the southwestern part. The northern section pre- 
sents much similarity to the New York section, though with more 
limestone, until we reach Devonshire, which is more arenaceous 
than the New York area, and still farther north in Scotland is 
represented by the old red sandstone, which may be likened to 
the sandstone part of the Gaspe section. But in Asturia, the 
Spanish area, according to Barrois the Devonian is mainly lime- 
stone, the divisions are less marked, and even the peculiarities 
observed in the fossils of Iowa as compared with New York rep- 
resentatives are shown, as in the variations of a single type of 
Spirifera disjuncta. 
§ 6. Problems for Settlesient. 
In regard to the Devonian, its nomenclature and classification, 
we find in the United States that there are three or four problems 
of general interest concerning which it devolves upon this com- 
mittee to give an opinion : 
(1) The Name. — Shall we follow the general usage and adopt 
the name Devonian system, with the area of Devonshire and 
Cornwall, England, as the typical area, and the paper of Sedg- 
wick and Murchison as the classical description of what the 
system is? 
(2) The Limits of the System. — This involves the determination 
