38 [Assembly 



the next above affords lead ore ; but the great depositories of this 

 mineral in Wisconsin" belong to a higher rock.) 



The Calciferous sandstone contains a considerable number of 

 fossils, which are described and figured in the first volume of 

 Professor Hall's Palseontology of New-York (the same volume 

 embracing the fossils of all the strata up to and including the 

 Hudson-river group). Among them are many obscure forms, 

 which are thought to be the remains or impressions of fuci or 

 marine plants (though their true nature is not always clear), 

 and which go under the general name offucoids. There are also 

 a few shells, nearly all of coiled forms, but they are rare in most 

 localities. It is interesting to know the earliest forms in which 

 this class of animal life appeared : they were those known to 

 scientific men as Euomphalus, a shell coiled nearly in a horizontal 

 plane ; Ophileta, a very similar but obscure form ; and Maclurea, 

 the characters of which are mentioned in describing the next 

 rock. This rock also contains a few generally imperfect shells 

 of the peculiar family to which the name of Orthoceras* has been 

 given. Their character and structure will be explained in speak- 

 ing of the Black-river limestone. 



The variety of living things which existed in the sea from 

 which this rock was deposited, does not appear to have been 

 large ; and so far as we yet know, it embraced no type of higher 

 order in the scale of life than the inhabitants of the coiled or 

 bivalve shells, or the animal inhabiting the shell of the Ortho- 

 ceras, which was a mollusc f of higher organization, something 

 like the cuttlefish of the present day. 



Next above the Calciferous sandstone, we find a dark, irregu- 

 lar, thick-bedded limestone, called, from the locality where it is 

 best seen (in Clinton county), the 



CHAZY LIMESTONE. 



Dr. Emmons states its thickness at 130 feet on Lake Champlain ; 

 but, in striking contrast with the wide extent of many other 

 rocks, it is known only in the Champlain valley, and does not 

 appear to extend in any considerable thickness into those parts 

 of the State west or south of the Adirondack region; and it is 



* Orthoceras, from the Greek orthos, straight, and keras, a horn ; referring to the straight 

 and tapering form of the shell . 



f Molluscs are soft-bodied animals, most of which, like the oyster, inhabit shells ; though 

 manj are naked, such as some snails, slugs, and the common cuttlefish or sepia. 



