16 



Bone beds, however, in their original state have furnished httle to 

 commercial supplies of phosphatic products, except those found in the 

 Tertiary and Quarternary ages, such as Bordeaux, Carolina, Florida 

 and Sombrero (breccia). 



SHELL BEDS. 



Since these must have existed from a time well into the 

 Paleozoic periods, or that is to say, from the Cambrian age, we may 

 expect and do find these mollusca remains, through a wide range of 

 systems and strata and up to recent times. 



The Silurian Lingula beds are remarkable, and have been already 

 particularized as a probable abundant source of phosphoric acid. 



The Welsh Silurian beds, and the French Bellegarde and 

 Ardennes deposits in the lower Green-sand (Cretaceous)^ exhibit 

 evidence of this origin, while the Tertiary and Quaternary phosphates 

 contain very frequently these marine and fluvatile remains as a 

 contribution to their value in phosphate of lime. 



Some very interesting specimens are on the table from the Dutch 

 West Indies, containmg from 75 to 80% of tribasic phosphate of lime, 

 and exhibiting in some cases, one mass of shells belonging to recent 

 times, 



COPROLITES. 



Owe their name to Professor Henslow, and should be applied only 

 to the fossil exuvise of animals. The appelation has extended itself to 

 many rolled or gravelly products, chiefly found in the Cretaceous form- 

 ation. In England they have been worked to a large extent in Bedford- 

 shire and Cambridgeshire, where they appear in the (Neocomian) 

 strata, between the chalk and the subjacent Jurassic system, in nodules 

 and pebbles of size from a pea to a hen's egg, and sometimes cemented 

 by ferruginous sand into a hard conglomerate; organic remains are 

 present, and casts and fragments of fossils with abundance of ammonites, 

 vegetable remains and other debris of the Jurassic epoch, {Igiianodon 

 and Megalosautus, etc.). 



The comr tercial products contain from 45 to 55% phosphate of lime. 



The Coprolites of Suffolk occur in the Tertiary, being in the older 

 Pliocene (the Red Crag and Coralline Crag). They are poorer in 

 phosphate of lime, more ferruginous and harder in texture. 



