No. 50.] 
393 
These groups are found in greater or less perfection throughout the 
fourth district ; their maximum thickness is probably in the Genesee 
valley, from which place they gradually diminish in thickness east and 
west* 
At the commencement of my labors the past season, my first object 
was to ascertain, if possible, a definite termination to the upper groups 
noticed in the report of last year, and also, something which would 
show more clearly and conclusively the connexion of these groups with 
the coal measures, as well as the characteristic and decided separation 
of the two. In following up the Tioga river beyond the limits of the 
State of New- York, I found the Chemung group succeeded by a red 
sandstone, which for the most part would pass for a rock destitute of 
fossils, but which however contains some peculiar remains which will ♦ 
be noticed directly. The commencement of this rock, and the upper 
limit of the group below, is well exhibited near Tioga, Pa. and also 
near Covington. Above the red sandstone we have greenish and grey 
sandstones which are succeeded by the rocks containing coal. 
To Mr. Taylor is due the credit of pointing out the existence of this 
rock, and its analogy to the old redsand stone of Europe. This analo- 
gy is farther confirmed by the fossil remains of the rock, which I be- 
lieve have never before been noticed. In tracing this rock westward 
we find it bordering the southern limits of the State and in Alleghany 
CO. extending north of the line. It apparently thins out in this direc- 
tion as the only representative we find of it on the Genesee river is a 
mass of about six inches thickness, containing a large proportion of iron 
in its composition which gives it more the appearance of an iron ore 
than a sandstone* 
In several places where this rock is exposed along the Tioga ri- 
ver, it contains fragments of bones, and scales of a fish, which prove 
on comparison to belong to the Holoptychus nobilissimus, of Agassiz, 
and which is a characteristic fossil of the Old Redsandstone, of Eng- 
land. It contains also the remains of another fish, the scales of which 
are larger than those of the Holoptychus. These scales in form re 
semble those of the Lepidotus. The length of the scale is two inches, 
and the breadth exceeds an inch and a half. Tlie broader and greater 
part of the scale is covered with a substance resembling shagreen^ 
while the narrower portion is slightly punctured as if small spines or 
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