_GEOGNOSY OF THE APPALACHIANS. 473 
latter, according to him, are seen to pass for considerable distances 
beneath nearly horizontal layers of the Red sandrock, the Utica 
slate, in one case, holding its characteristic fossil, Triarthrus Beckii. 
This relation, which is well shown in a section at St. Albans, fig- 
ured by Hitchcock,* was looked upon by Emmons and by Adams as 
evidence that the Red sandrock was the representative of the Me- 
pas sandstone of the New York system. When, however, the 
rmer had recognized the Potsdam age of the sandrock, with its 
oe which he supposed to be Paradoxides, this condition of 
things was conceived to be an evidence of the existence beneath 
the Potsdam of an older and unconformable fossiliferous series 
already mentioned. 
The objections made by Emmons to Rogers’s view of the Cham- 
plain age of the Taconic rocks were three-fold : first, the great dif- 
ferences in lithological characters, succession and thickness, be- 
tween these and the rocks of the Champlain division as previously 
known in New York; second, the supposed unconformable infra- 
position of a fossiliferous series to the Potsdam ; and third, the dis- 
tinct fauna which the Taconic rocks were supposed to contain. The 
first of these is met by the fact now established that in the Appa- 
lachian region, the Champlain division is represented by rocks 
having, with the same organic remains, very different lithological 
characters, and a thickness ten-fold greater than in the typical 
Champlain region of northern New York. The second objection 
has already been answered by showing that the rocks which pass 
beneath the Potsdam are really newer strata belonging to the upper 
part of the division, and contain a characteristic fossil of the Uti- 
ea slate. As to the third point, it has also been met, so far as 
regards the Atops and Elliptocephalus, hy showing these two 
genera to belong to the Potsdam formation. If we inquire farther 
into the Taconic fauna we find that the Stockbridge limestone (the 
Eolian limestone of Hitchcock), which was placed by Emmons near 
the base of the Lower Taconic, (while the Olenellus slates are 
near the summit of the Upper Taconic), is also fossiliferous, and 
contains, according to the determinations of Professor Hall, species 
_ belonging to the genera Euomphalus, Zaphrentis, Stromatopora, 
to the 
Chaetetes and Stictopora.t Such a fauna would lead con- 
Geology of Vermont, p. 37: 
t Geology of Vermont, 419, a Amer. Jour. Sci., I, xxxiii, 419. 
