The American Geologist. December, 1903. 
These Pennsylvanian fossils are the oldest indications of 
vertebrate existence that the rocks have yet yielded, regarding 
whose nature and horizon no doubt can be entertained. The 
reported discovery some years ago "l" fossil fishes in Ordovician 
strata in Colorado, on which a paper was read before the Inter- 
national Congress of Geologists, at Washington, in 1891, is 
apparently too uncertain for confidence and its accuracy must 
be considered as questionable.* 
After very careful examination of specimens from the lo- 
cality and as much study of the stratigraphy as can well be 
made at second hand, I can not avoid the conclusion, forced 
upon me by microscopic and other study of the fragments of 
bone and comparison of the published figures, that these fos- 
sils are Devonian in age and must be correlated with others of 
that era and that the red sandstone in which they occur cor- 
responds with the well known Old Red sandstone of Scot- 
land and has been in some way displaced and possibly over- 
thrown by faults and thrusts. The stratigraphy of the region 
is manifestly complex and much disturbance has taken place, 
rendering the utmost caution necessary and the most rigid 
proof indispensable. 
VI. ON THE PERSISTENCE OF FAUNAS IN 
THE DEVON I AX. 
The facts that were given in a previous section illustrate 
strongly the danger of too close a correlation of non-adjacent 
areas, even when separated by no very long distance. The 
characteristic Marcellus fauna of New York appeared in the 
thin shaly bed found by Whitfield near the middle of what had 
been considered the Corniferous limestone in Ohio, and is 
succeeded above by a profusion of typical Corniferous fossils, 
which are not known on a similar horizon in New York. The 
oh\ion> inference is that, while the Marcellus fauna occupied 
the inner part of the Appalachian gulf to the exclusion of the 
1. oiuiferous species, the latter were predominant Jn the mouth 
o* the same gulf. It is further to be inferred that small and 
* In spite of the apparent connection of the argument in Mr. Wnlcott's 
paper, much closer and more cogent reasoning will be required to convince 
palaeontologists of the Ordovician age of the fossils and to overcome their 
repugnance to setting back so far at a bound the epoch of the commencement 
of vertebrate existence. The sections, too, must be more strictly connected 
with one another and the absence of any disturbances and irregularities en- 
sured. 
