io88 PRINCIPLES OF STRATIGRAPHY 



which they occur loose in the gauge of the ore-beds. (Blum- 

 4:^09.) 



(h) Vertebrates. The bones of vertebrates contain much cal- 

 cium phosphate with the calcium carbonate, the whole being bound 

 together by the organic ossein, or bone-cartilage. According to 

 Berzelius, the bones of mammals consist of: bone cartilage 32.17 

 per cent. ; ducts 1.13 per cent. ; basic phosphate of lime with a trace 

 of fluoride of calcium, 54.04 per cent.: carbonate of lime, 11.30 per 

 cent.; phosphate of magnesia, 1.16 per cent.; and carbonate of 

 sodium with a trace of the chloride, 1.20 per cent. The organic 

 substance is replaced by the mineralizer, which is commonly calcium 

 carbonate. Sometimes complete crystallization takes place. Among 

 the bones found in the gypsum beds of the Paris basin and other 

 regions many had been more or less impregnated with gypsum. 



Pyritized skeletons of Ichthyosaurs, Plesiosaurs and other rep- 

 tiles, as well as higher types, are common. Where marcasite is the 

 replacing agent decomposition readily sets in and, if the matrix 

 is a clay slate (argillutyte), alum efflorescence marks the progress 

 of this decay. 



Chalcopyrite is common as a coating of fish remains in Thur- 

 ingia and Hessia, though seldom wholly replacing them. Bornite 

 occasionally performs the same office. Native copper sometimes 

 results from the alteration of these coatings. Cinnabar sometimes 

 occurs in the same manner as the copper ores, seldom completely 

 replacing the fish remains. 



The teeth of mammals are rich in phosphate of lime, 60 per 

 cent, or more of this salt being present. To the large proportion 

 of this substance the durability of the teeth is attributable, they 

 being among the most frequently preserved parts of mammals. The 

 enamel of the teeth contains a somewhat larger percentage of phos- 

 phate of lime than the dentine, a dift'erence which is expressed in 

 the diverse degrees of preservation of these parts. (D'Orbigny- 



11:5;-) 



Eggs of vertebrates have not infrequently been found well 



preserved. Examples are: the eggs of the Moas of New Zealand, 



Chelonian eggs from the Tertiary of Auvergne, France, in which 



the shell was filled with mud which subsequently hardened ; the 



Miocenic egg from South Dakota described by Farrington (12), 



which was completely silicified, and the fossil egg of Quaternary 



age from Arizona, described by Morgan and Tallmon (18), in 



which the shell is perfectly preserved, showing the same structure 



found in modern hen's eggs, the shell agreeing in composition 



with that of the egg of the wild goose. The interior with the 



