SPIRIFERiE OF THE PORTAGE AND CHEMUNG GROUPS. 237 
SPIRIFERiE OF THE PORTAGE AND CHEMUNG GROUPS. 
.The shales and sandstones of the Portage group, within the limits of the 
State of New-York, are generally very deficient in Brachiopoda, and but 
a single species of Spirifer is at present known to me in this formation. 
This one is more like the European Carboniferous Spirifera glabra, than 
any of the Devonian species figured by Mr. Davidson in his Monograph 
of British Devonian Brachiopoda. 
In the Chemung group, Brachiopoda are abundant, and Spirifera is 
very conspicuous among the other genera. Notwithstanding however its 
abundance and wide distribution in this group, there are few species 
known in the State, and of these, one only is common, the Spirifera verneuili 
— S. disjuncta and its varieties, which extends from the southeastern 
counties quite to the western limits of the State, and is equally abundant 
in the adjacent portions of Pennsylvania along the southern and western 
borders of New-York. 
I have heretofore recognized, with doubt, the Spirifer mucronata* in 
the Chemung group in the southern part of New-York; but a critical 
examination of all the specimens from authentic localities of that forma¬ 
tion has shown that the fossils thus referred belong to the S. mesacostalis, 
and no true example of S. mucronata is yet known to me from the Che¬ 
mung group. 
It may be remarked in this place that the shaly sandstones or arena¬ 
ceous shales of the Hamilton group in the southeastern part of the State 
are lithologically similar to some of the Chemung beds, and not always 
readily distinguishable therefrom. In these coarser beds of the Hamilton 
group, the S. mucronata is often abundant in the condition of casts. 
Delthyris mucronata ? Geological Report of the Fourth District of New-York, p. 271. 
