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Produdus. An extinct genus of fossil bivalve shells. 



Plastic Clay. One of the beds of the Eocene period. The plas- 

 tic clay formation is mostly composed of sands with associate beds of 

 clay. 



Pud Jin g Stone. See Conglomerate. 



Pyrites. A mineral, composed of sulphur and iron. It is usually 

 of a brass yellow, brilliant, often crystallized, and frequently mistaken 

 for gold. 



Quartz. A simple mineral, composed of silex. Rock crystal is an 

 example of this mineral. 



Pock. All mineral beds, whether of sand, clay, or firmly aggregated 

 masses, are called rocks. 



Saiuhlone. A rock composed of aggi-egated grains of sand. 



Savria'is. Animals belonging to the lizard tribe. 



Schist. Slate. 



Seams. "Thin layers which separate strata of greater ma:Tnitude." 



Secondary Strata. "An extensive series of the stratified rocks, 

 which Compose the crust of the globe, with certain characters in com- 

 mon, which <li)^tin:Tuish ihem from another series below them, called pri- 

 mary, and another above ihem, called tertiary." 



Sedimentary Rocks, aie those which have been formed by their ma- 

 terials having been thrown down from a state of suspension or solution 

 in water. 



St'lniite. Crystallized gypsum. 



Septaria. Flattened l)alls of stone, which have been more or less 

 cracked in different directions, and ceu)ented together by mineral mat- 

 ter which fill the fissures. 



S"rpentine. A rock composed principally of hydrated silicate of 

 magnesia. It is generally an unstralified rock. 



Shale. An indurated slaty clay, which is very fissile. 



Shell Marl — Fresh water Shell Marl. A deposit of fresh water 

 ghellf, which have disintegrated into a gray or white pulverulent mass. 



Shingle. The loose water-worn gravel and pebbles on shores and 

 coasts. 



Silex. The name of one of the pure earths which is the base of 

 flint, (piariz, and most sands and saudstones. 



Silicious. Containing silex. 



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