60 Review of the New York Geological Reports. 
members, and those now under consideration, the upper beds of 
one and the same group ; indeed in Pennsylvania and Virginia all 
are included in Formation 8. The New York geologists have 
separated them only because some of the fossils are peculiar to 
the Marcellus shales, and some to the Hamilton beds. 
The various members embraced in the latter division, are :— 
Pyritiferous rock and third graywacke of Katon ; Ludlowville, 
Moscow, and. Skaneateles shales ; dark slaty fossiliferous shales ; 
compact calcareous blue shale; olive shales, shales near Apulia 
and Sherburne ; Cazenovia group, Encrinital limestone. Under 
these names have they been noticed in the Annual Reports. 
Dull, olive, bluish-gray, calcareous shale constitutes the prin- 
ciple mass. 'The mud from which it has been derived must have 
been equally fine with that of the previous group, indicating a * 
continuation of the tranquil condition of the oceanic currents. 
owards the east the upper part is more arenaceous, even a reg- 
ular sandstone. 
The range, extent, and bearings are south and nearly parallel 
with the preceding strata; indeed on the marl the same light 
blue tint designates all, from the base of the Marcellus shale to 
the Portage group, and embraces a belt of country from five to 
ten miles wide running nearly east and west through the middle 
of the state. : 
The Hamilton group is of great thickness. Vanuxem informs 
us that in no part is it less than three hundred feet, and it swells in 
some places to seven hundred feet; and Hall estimates it on the 
eastern limit of his district at not less than one thousand feet. 
The town of Hamilton, in Madison county, gives name to 
the group, and it is one of the best localities for examining its 
most i ant members. The bank of Cayuga and Seneca 
the ravines on the Genesee river near Avon, York, an 
eicester, the shores of Lake Erie at Kighteen-mile creek; the 
hills on both sides of Cherry Valley, Middlefield, Milford, Otsego, 
Brookfield, Cazenovia, Lafayette, Pompey, Owasco, are enume- 
rated by Vanuxem and Hall as points where its various members 
Mig ee 
Septaria of very curious and fantastic shapes are of frequent 
occurrence ; so wonderfully regular are some of them that they 
are usually taken for petrified: turtles. 'The nucleus is either a 
fossil body or a nodule of iron pyrites around which. the segre- 
gration has taken place. 31 wis 
' Speaking of the general character of ‘the fossils of the Hamil- 
ton group, Hall has the following paragraph :— : 
“Organic remains abound throughout the group, but they vary 
somewhat in different parts. In the lower division, the most 
sare those of Orthis, Atrypa and Strophomena with 
some spiral univalves; while above this portion, great numbers 
