ONONDAGA LIMESTONE. 133 



There are many fossils by which this rock is readily recognized, and are characteristic of 

 it, besides the Encrinites laevis. Among them is the Elongated pentamerus (No. 1 of the 

 wood-cut). This fossil is generally diffused in this rock, and so far as our knowledge of it 

 extends, is confined to it. Some of the specimens show a considerable size, being about 2^ 

 inches in depth or thickness, and 4f inches in length. The Undulated delthyris, which 

 resembles the Thick-ribbed delth5ms, is also found in it ; but the ribs are not so round, and 

 the surface is covered with undulations in the direction of the lines of growth, whence its 

 name. It contains also the Consimilar hipparionix (No. 3 of the wood-cut), which is also 

 found in several localities. It is the only rock in which the Gigantic cyathophyllum (C. 

 gigantea) is found ; one of which, in the State Collection, is over eight inches in length and 

 two and a half in diameter. There are four other species of this genus in the collection 

 from this rock ; about three species of the Platyceras, three of the Platyostoma, and several 

 other fossils which are new, among which is the fish-bone (No. 4 of the wood-cut). This is 

 the first rock in the district, in which any thing of the kind had been seen or heard of. In 

 the State Collection there is another one from the fourth district, but very imperfectly pre- 

 served, found by Mr. Hall in the Qriskany sandstone, the lowest position in which any 

 remains in the State have been discovered of an animal higher in the scale of organization 

 than Crustacea, or the class to which crabs, lobsters, etc. belong. There are fish bones of 

 like character in the State Collection, obtained from the next rock in succession in both dis- 

 tricts ; all which seem to have served a common purpose, appearing to be the major spine of 

 the back or dorsal fin. 



The layers and courses of this limestone, as usual with limestone rocks, are separated by 

 shale, which is of a greenish color, but in small amount. It is coextensive with the rock, a 

 fact of some importance in the theory or cause of the color of rocks ; for the less the crystal- 

 line action, the more the red, black and yellow colors predominate, crystallization favoring a 

 lower degree of oxidation of the metallic coloring matter. 



The Onondaga limestone, though generally nearly pure, in some localities contains nimie- 

 rous nodules of flint, and in parallel layers. Its vertical joints are very regular in two direc- 

 tions, at nearly right angles to each other, often dividing the layers into convenient sized 

 masses : direction of the joints, N. 33° to 35° E., and S. 55° to 57° E. 



It is one of the most valuable building stones in the Helderberg division. It is largely 

 quarried near Syracuse for the canal, and is more or less used as a marble throughout the 

 district. Its power to resist the action of air, water and frost, is shown from the fact of its 

 being the bottom rock of streams which no longer exist ; and it is the rock generally over 

 which the water flows north, forming the falls great and small at the west end of its range, 

 the most noted of which are those of Perryville and Cazenovia. 



This limestone forms a conspicuous ledge of about twelve feet thick to the right of the road 

 from Fort-Plain to Cherry- Valley, the surface of the rock being uncovered for some extent. 

 It continues to the village, but is concealed in part of its course by alluvion thrown up into 

 low hills. It forms the surface of the valley, and is uncovered in many parts above the road 

 which crosses the valley towards the lower part of the village. The north projecting end 



