18 RHIZOPODA. 



also on the bottom, even at a depth of 12,000 feet. From 

 these great depths they are procui-ed by soundings ; the 

 sounding-lead, after being coated with grease, brings up 

 attached to it the small particles with which it comes in 

 contact. Numerous such soundings were taken by Sir 

 James Ross in his Antarctic expedition, and have been 

 practised by others in different regions. Dr. Barclay 

 records the results of a series of deep sea-soundings 

 made in the Atlantic, over a considerable geographical 

 area, from latitude 42° 4' to latitude 54° 17' at depths 

 varying from 1,080 to 2,000 fathoms. "None of the 

 soundings contain a particle of gravel, sand, or other 

 unorganized matter. They all agree in being made up 

 entirely of the shells of Foraminifera." There is, there- 

 fore, little doubt that the bottom of the ocean is in many 

 localities covered, perhaps to considerable depths, by 

 a sedimentary deposit, consisting jjrincipally of shells 

 of this description, and vvhich, were they raised to the 

 surface, would constitute thick beds of incalculable ex- 

 tent. 



In a fossil condition, the shells of the Foraminifera 

 enter largely into the composition of the crust of the 

 earth in every part of the world. They form by far the 

 most important constituent of chalk wherever that sub- 

 stance is met with. Dr. Barclay speaks of them as im- 

 portantly concerned in the formation of the tertiary rocks 

 of South Carolina, and adds, " they are still at work in 

 countless thousands on that coast, filling up harbours, 

 forming shoals, and depositing their shells to record the 

 present state of the sea-shore as their predecessors, now 

 entombed beneath Charlestown, have done with regard to 

 ancient oceans." 



In many parts of the world the accumulation of these 

 shells has given origin to widely-extended strata, many 

 hundreds of feet in thickness. Mountains of Nummulitic 

 limestone, entirely composed of them, extend through the 

 Alps and Northern Italy, and are met with in Greece, Syria, 

 and Northern India The Mokkadam range, from which 

 the stone used in building the Pyramids was obtained, are 

 simply masses of foraminifcrous shells. According to 

 M. Deshayes, there is found in most of the stone from 

 which Paris is built, as large a proportion of the shells of 

 Foraminifera as of particles of sand, so that it may be 

 said, almost without exaggeration, that even Paris owes 



