52 FOSSIL FORAMINIFERA. PART in. 



vicinity of the West Indian Islands, on both sides of 

 South America and near the Isle of France, but not in 

 the Coral Sea which is occupied by different genera. 

 Though in utter darkness, at the bottom of a deep 

 ocean, these little creatures can procure food by means 

 of their pseudopodia, whose extreme sensibility makes up 

 for the want of sight ; and the very excess of pressure 

 under which they live insures them a supply of oxygen 

 at depths to which free air cannot penetrate, for it is 

 believed that the quantity of dissolved air that water 

 contains is in proportion to the pressure. 



Fossil Foraminifera enter so abundantly into the 

 sedimentary strata, that Buffon declared ( the very dust 

 had been alive.' 58,000 of these fossil shells have been 

 computed in a cubic inch of the stone of which Paris and 

 Lyons are built. The remains of these Ehizopods are 

 for the most part microscopic. M. D'Orbigny estimated 

 that an ounce of sand from the Antilles contained 

 1,800,000 shells of Foraminifera. A handful of sand 

 anywhere, dry sea-weeds, the dust shaken from a dry 

 sponge, are full of them. 



When the finer portions of chalk amounting to one 

 half or less are washed away, the remaining sediment 

 consists almost entirely of the shells of Foraminifera, 

 some perfect, others in various stages of disintegration. 

 In some of the hard limestones and marbles, the relics 

 of Foraminifera can be detected in polished sections 

 and in thin slices laid on glass. It is now universally 

 admitted that some crystallized limestones which are 

 destitute of fossil remains, had been originally formed 

 by the agency of animal life, and subsequently altered 

 by metamorphic action ; the opinion is gradually gain- 

 ing ground among geologists that such is the history of 

 the oldest limestones. 



At certain geological periods circumstances favoured 

 the development of an enormous multitude of indivi- 



