132 AQUEOUS EOCKS 



matter and acids, 11.3%; ammonia (carbonate, etc.), 31.7% 

 fixed alkaline salts, sulphates, phosphates, chlorides, etc., 8.1% 

 phosphates of lime and magnesia, 22.5% ; oxalate of lime, 2.6% 

 sand and earthy matter, 1.6%; water, 22.2% (Geikie). Copro- 

 lite nodules are likewise the excrements of vertebrate animals; 

 those among the Carboniferous shales of the basin of the Firth 

 of Forth are regarded as accumulated excretions of ganoid fishes. 

 Phosphatic sandstones, as the name denotes, are arenaceous 

 rocks containing more or less phosphatic matter. Inasmuch as 

 the phosphatic material is derived largely by leaching and 

 segregation, these rocks have been already described under the 

 head of chemical deposits (p. 111). In the river beds of the 

 Eastern Carolinas are found rounded and nodular masses of this 

 nature, consisting of siliceous and calcareous sand, with em- 

 bedded bones, teeth of sharks, and other animal remains. Bone 

 breccia consists of fragmental bones of mammals cemented by 

 argillaceous, earthy, or calcareous matter. 



