catskill shaly limestone. 
121 
district as to thickness, and fossils as to kinds. It is, however, well exhibited to the north of 
Cherry-Valley in ascending the hill or ridge, and in the road to Judd’s mill, etc.; also through 
the towns of Warren and Columbia in Herkimer county. In Oneida county, but little com¬ 
paratively is seen, the ridge being broken by the Sauquoit and other creeks, and the lime¬ 
stone concealed by its overlying rocks, and by drift and soil. 
It appears, however, to be in considerable thickness at Oriskany falls ; the greater part a 
pretty good limestone, parts only showing admixture of a brown or lighter colored shale where 
long weathered. Fossils are not numerous at this locality, excepting in the upper part, just 
below the Oriskany sandstone. From the absence of shale, and from the fossils in this rock 
and in the pentamerus under it being but few comparatively in number, the line of division 
is quite obscure at the falls ; so much so, that no attempt was made to ascertain its existence ; 
whereas at the east, it is well defined, the shaly layers commencing with the Catskill creek 
rock, and their fossils being in profusion. 
The Catskill shaly limestone, as repects fossils, is of great interest; they are so numerous, 
and so varied; and no doubt when the divisions of the Transition class are more attentively 
examined elsewhere, it will be found, as well as most of the other members of the New-York 
system, to be more generally diffused than at present supposed, or rather made known. 
But a few only of its fossils are given for illustration. The Big-ribbed delthyris (No. 1 of 
the wood-cut) is in great number in the first district, and so also is the Thick-winged delthyris 
(D. pachyoptera), from whence the first name of the rock was in part derived. They both 
occur at the east end of the district, but soon disappear or run out, and both occur in the part 
where shale greatly predominates. They occur in Pennsylvania ; and in the Chinese museum 
recently established in Philadelphia, there was a delthyris from China, which greatly resem¬ 
bled the pachyoptera. 
No. 2. The Smooth atrypa is in great abundance, especially in Herkimer county; and it 
appears to be numerous at Oriskany falls, just under the Oriskany sandstone, which covers 
that part of the rock containing them. A specimen was seen showing that a slight sprinkling 
of sand existed in the limestone which covered the shells, being the beginning of a change, or 
apparition of a power, which, like the wand of the enchanter, put an end almost wholly to all 
the tenants of the argillaceous and calcareous masses of the Catskill rock in Ncw-York, and 
ushered in another series, no less extraordinary than those whose existence was thus ended. 
The Smooth atrypa, throughout the range of the Oriskany sandstone, was seen only in a loose 
mass in Otsego county. 
No. 3, belongs to another division of atrypa, which, like those of this genus already noticed, 
also merits attention. The valves of this division are very unequal; the upper one is flat, and 
forms with the end opposite to the beak, nearly a right angle ; the lower valve curves from the 
beak to the straight line on the opposite side. The middle or mesial part is very much 
depressed. There are about four species of this division in the State, one of which only has 
been named by Mr. Conrad, namely, the peculiaris, and which belongs to the next rock in' 
succession, the Oriskany sandstone. The species of the wood-cut is more remarkable; and 
to show their allied nature, the name of Singular is proposed (A. singularis). Size natural. 
Geol. 3d Dist. 16 
