CATSKILL SHALT 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 Philjulelphia, 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 New-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 atrjrpa, 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 



