No. 50.] 
203 
parated from it by five formations. 1. A blue limestone well marked 
by the remains of a large species of Crinoida resembling a Scutella in 
form. 2. Oriskany sandstone, with a most singular group of large bra- 
chiopodous bivalves, of which not one is figured by Murchison. 3. Fu- 
coidal brown sandstone. 4. Grit, which is the Lower Ludlow rock of 
Murchison. 5. Black limestone. 
Lower Ludlow Rock 
The position of this I have indicated above, but there are other for- 
mations higher in the scale which have different fossils, yet evidently 
analogous to those of the Lower Ludlow rocks. The comparative list 
in the grit is as follows : 
•N 
Shells. 
Phragmoceras arcuatum, Lituites biddulphii, Orthoceras pyriforme, 
Spirorbis tenuis. 
The Lituites biddulphii has the spirorbis impressions upon it just 
like the specimen figured by Murchison. 
One of the finest geological sections in the whole range of the Silu- 
rian system occurs at Schoharie, where fortunately the organic remains 
have been collected in great numbers by my friend John Gebhard, Jun. 
whose zeal is worthy of all praise. Through him I have obtained rare 
and valuable specimens for the use of the survey, and still more valua- 
ble information regarding the stratagraphical position of some of them. 
It may be interesting to some persons to have a knowledge of this sec- 
tion, and I therefore subjoin it, and embrace some of the fossils of the 
Helderberg in the same table. 
Black slate, , Posidonia, Orthoceras linteum. 
Gra limestone \ Odontocephalus selenurus, (Asaphus, Eaton,) 
y ) Platyceras dumosum, Delthyris acuminata. 
Blue limestone, ...A ^a^sites gothlandica Cyathophyllum vermicu- 
i tare, feyrmgipora biiurcata f 
Black limestone \ Calymene Rowi, Asaphus laticostatus, Atrypa 
' " " ^ naviculoides. 
r Calymene platys, Lituites biddulphii, Phragmo- 
Grit, < ceras arcuatum, Orthoceras pyriforme, spi- 
( rorbis tenuis, Pleurorhyncus cuneus. 
Brown sandstone, . . . Fucoides cauda-galli. 
Oriskany sandstone, \ ^^'^P^ elongata, Delthyris arenosa, Strophome- 
' ' ^ na unguitormis. 
