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sils most abundant are Delthyiis striatula? Atrypa concentrica, and A» 
affinis, CyathophyliteS; fragments of Trilobites, &c. 
V. Ludlowvilk shales. The fissile olive shale, noticed as the southern- 
termination of the last described mass, passes into a more compact 
form, retaining the colour, &c. but characterized by an entirely different 
association of fossils. Its upward limit is well defined by a mass of 
limestone, which contains abundance of encrinal columns. The most 
characteristic fossils are several species of Pterinea, and a peculiar Lep- 
taena, which has not been seen in any other rock. This shale is exposed' 
from one to three miles north of Hathaway's landing, in Baileytown, 
on Seneca lake 5 it also appears in all the ravines which come into the 
lake near this place. 
The same shale is exposed along the lake shore in Cayuga county, 
near Ogden's ferry, and at Ludlowville. The various species of Pteri- 
nea are much more abundant at these localities than any yet seen in the 
Fourth District. 
The Encrinal limestone, the terminating rock of the shale last de- 
scribed, maintains a very uniform and constant character from Cayuga 
lake to the Genesee river. It never attains a thickness of more than 
four feet; sometimes it is divided into two or three courses, at other 
times it consists of one only. It abounds in fragments of Encrinal co- 
lumns, some of which are an inch in diameter, and from half an inch 
to one or two feet in length. There is occasionally found in this rock 
a large Leptaena, and Delthyris, Cyathophilli, &c. no other fossil, how- 
ever, than the crinoidal columns being constant. The rock is generally 
tough, and not readily affected by the weather, standing out in bold relief 
from the surrounding shales. It can be seen in the bank of Seneca 
lake, one mile north of Hathaway's landing, and about the same lati- 
tude on the Cayuga lake side of the county. 
VI. Moscow shales. Above the encrinal limestone the character o^ 
the fossils and shale is considerably changed. The principal part of the 
mass is of a bluish colour, sometimes olive, and in certain localities por- 
tions near the upper part are black. Very little of the whole mass is 
slaty; it generally separates into irregular fragments, and is traversed by 
seams in various directions. The lower part sometimes contains fine 
fossils, but the upper portions are the most prolific in fossils of any rock 
in the district. Most of the shale is highly calcareous, forming by its 
disintegration a very fertile soil; it is readily affected by atmospheric 
agents and rapidly decomposed. Along the banks of the lake, and in 
