PALEONTOLOGY OF NEW-YORK. 3 
Dalmania and Phacops are remarkable for their spiniferous character ; 
while the Lichas and Acidaspis, yet known only in fragments, are of 
the most extravagant forms of those genera. 
Whatever may be the ultimate decision relative to the line of separa¬ 
tion between Silurian and Devonian systems, the base of the Schoharie 
grit offers a much more decided limitation below, than does the Oriskany 
sandstone. The new fauna bears less relation to the preceding, and many 
of the new types are of a strikingly distinct character. In the Oriskany 
sandstone, we have a considerable number of species which first appear 
in the Lower Helderberg group; and the connection between these two 
formations is much more intimate than between the Oriskany sandstone 
and the Schoharie grit. 
Since the faunae of the Schoharie grit and of the succeeding forma¬ 
tions, more especially as far as the Hamilton group inclusive, have so 
many features in common, I have grouped the fossils together, with a 
view to a more perfect zoological arrangement; and, in the first place, 
I introduce the Brachiopoda of all these formations, designating under 
each description, as well as in the title of the plate, the rock from which 
they have been derived. 
In arranging the plates, I have followed to some extent the order in 
which the fossil genera appeared in time, taking care nevertheless to 
preserve the proper zoological arrangement. The following pages, there¬ 
fore, with the accompanying plates, will present a pretty full illustration 
of the Brachiopoda now known in these groups, before named, within 
the State of New-York. 
I have sometimes found it necessary to go beyond the limits of the 
State, to secure specimens fit for the illustration of species known to 
occur within its limits; and a few extra-limital species have been intro¬ 
duced for the purposes of comparison. In doing this, however, I have 
taken great care, as I have always heretofore done, to avoid deriving 
specimens from any portion of the country, or any State, where surveys 
have been going on, in which a department of palaeontology has been 
organized, and whence we might have reasonable expectation of seeing 
the fossils described and illustrated. 
