36 [Assembly 



earliest and oldest fossil remains of once-living things. These 

 palgeozoic rocks have been again subdivided into four systems, 

 the lowest being called the Silurian, the next the Devonian ; the 

 Cauboniferous or Coal formation succeeding, and the Permian 

 being the uppermost. 



The fossiliferous rocks of New- York (with very limited excep- 

 tions which will be noticed) belong to the lower subdivisions of 

 the Palaeozoic strata, the Silurian and Devonian systems. The 

 oldest and lowest of them,* which is found in many places to 

 rest directly upon the gneiss, is a hard sandstone or quartz rock, 

 usually brownish in color, though sometimes of other shades, and 

 attaining in some places the thickness of 300 feet. Its edge can 

 be traced nearly all around the great hypogene and metamorphic 

 region of the Adirondacks, and is especially well seen near Keese- 

 ville in Clinton county, where the deep ravine of the Ausable 

 river is cut through it; also at Potsdam, St. Lawrence county, 

 from which place it is called the 



POTSDAM SANDSTONE. 



It is an excellent building material. Its fossils are very few, the 

 only distinct forms are a couple of species of minute shells of the 

 Genus Lingula, which are the oldest of our fossils. Specimens 

 of them may be seen in the case marked "Potsdam sandstone ;'' 

 in looking at which, the observer may be confident that he sees 

 some of the very earliest forms of animal life which were intro- 

 duced on our earth f (Pig. 1). This rock shows, on many of its 

 layers, waved surfaces, precisely resembling the ripple-marks seen 

 on sandy bottoms over which waters are agitated by waves or 

 currents. They are believed to have been formed in the same 



* Professor Emmons maintains that there exists in Eastern New-York a series of fossili- 

 ferous strata older and lower than the Potsdam sandstone ; which he calls the Taconic system, 

 but this is a controverted point. See some remarks on it hereafter in describing the *'Hudson- 

 river group." 



t We quote from Hugh Miller his popular description of this shell. " The Lingula 

 still exists in some two or three species in the distant Moluccas. There was but one of these 

 known in the time of Cuvier; and so unlike was it deemed to any of its cotemporary mol- 

 lusca, that of the single species he formed not only a distinct genus, but also an independent 

 class. The existing, like the fossil shell, resembles the blade of a shovel; but the shovei 

 has also a handle, and in this mainly consists its dissimilarity to any other bivalve. A cylin- 

 drical cartilaginous stem or footstalk elevates it some inches over the rocky base to which it 

 is attached, just as the handle of a shovel stuck into the earth would elevate the blade over 

 the surface, or as the stem of a tulip elevates the flower over the soil. I am not aware that 

 any trace of the cartilaginous footstalk has yet been detected in fossil Lingulae; but in all 

 that survives of them, or could be expected to survive, the calcareous shell, thoy ate iden- 

 tical in type "with the living moUnsc of the Moluccas." 



