60 LITHOLOGICAL GEOLOGY. 



called coprolites ; when in large accumulations (as sometimes made by 

 birds or bats), guano. 



The remains of animals have also afforded traces of fluorine. 



(4.) The carbonaceous, or those which have afforded coal, mineral 

 oil, and resin, as plants. 



Besides these, there is a fifth kind, though of little importance geo- 

 logically, viz., the animal tissues themselves. Only in a few cases do 

 any of these tissues remain in fossils, except in some groups belonging 

 to the later geological epochs. These tissues contain traces of j:>hos- 

 phates and fluorids which they have contributed to the muds of which 

 rocks have been made. 



(1.) Calcareous. — The following are a few analyses: 1 and 2, corals, Madrepora 

 palmata, and Oculina arbuscula by S. P. Sharpies (Am. Jour. Sci., III. i. 168) ; 3, 

 shell of a Terebratula, by the same: — 



Madrepora. Oculina. Terebratula. Oyster-shell. 



Carbonate of lime .... 97-19 95-37 98-39 93-9 



Phosphate of lime .... 0-78 0-84 \ 0-61 0-5 



Sulphate of lime .... - - > - 1-4 



Water and organic matters . 2"81 3-79 J 1-00 3-9 



Carbonate of magnesia . . - - - - 3 



In many shells, the inner pearly layer consists of carbonate of lime in the condition of 

 aragonite; while the outer (or the whole, if no part is pearly) is usually common car- 

 bonate of lime, orcalcite. The spines of fossil Echini axe. calcite. 



In corals of the genus Millepora, according to Damour, there is, besides carbonate of 

 lime, some carbonate of magnesia, amounting in one species to 19 percent., while but 

 little in others. These corals have been shown by Agassiz to be the secretions of Acalephs, 

 and not of ordinary polyps. Forchhammer found 6 - 36 per cent, of carbonate of magnesia 

 in the fsis nobilis, and 2-1 per cent, in the Corallium mobile, or " precious coral " of the 

 Mediterranean. 



The Nullipores and Corallines are vegetation having the power of secreting lime, like 

 the coral animals. The shells of Rhizopods (called also Polythnlamia and Fwaminifera) 

 are calcareous. 



The shell of a lobster (Palinurus) afforded Freiny, carbonate of lime, 49'0, phosphate 

 of lime, 6-7, organic substance, 44-3. 



(2.) Siliceous. — The organic silica is, in part at least, in that condition charac- 

 terizing opal (p. 53). This is the case with the siliceous spicula of sponges and with 

 diatoms. 



(3.) Phosphatic. — Analyses of bones: 1, 2. human bones, according to Frerichs; 3, 

 fish (Haddock), according to Dumenil; 4, shark (Squrtlus cornubicus), according to 

 Marchand; 5, fossil bear, id.; 6, shell of Lingida ovalis, Hunt. 



1. 2. 3 4. 5. 6. 



Phosphate of lime 50-24 59-50 55-26 32-46 62-11 8579 



Carbonate of lime 11-70 9-46 6-16) .,, 13-24 11-75 



Sulphate of lime - - - ) 1225 



Organic substance 38-22 3094 37-63 5807 4-20 



Traces of soda, etc - - 1-22 3 80 



Fluorid of calcium - - - 1-20 2-12 



Phosphate of magnesia ... - - - 1-03 0-50 2*80 



In Xo. 4, a little silica and alumina are included with the fluorid. No. 5 contains also 



