RHIZOPODA. 9 



The species are few in our seas ; but in those of 

 warm climates, as in the Mediterranean, they are 

 much more numerous ; but all the existing kinds 

 put together dwindle into insignificance when com- 

 pared to the almost incredible profusion in which 

 the Class existed in the ancient seas of the secondary 

 and tertiary epochs. Their fossil shells form 

 almost the entire bulk of extensive mountains ; 

 Paris is completely based on Foraminifera ; and 

 the extent to which they are crowded together 

 can only be compared to that of the grains in a 

 heap of corn. Plancus found 6,000 specimens in 

 an ounce of sand from the Adriatic, but D'Orbigny 

 estimates the same quantity of sand from the 

 Caribbean sea to contain the inconceivable number 

 of 3,840,000 shells ! It is needless to add that 

 these must be of excessive minuteness, as are most 

 of the recent species ; some of the fossil NummuUnce, 

 however, are of the size of a crown-piece. 



■Localities, &c. — The living species are found 

 adhering to sea-weeds, and branching zoophytes. 

 I have obtained Polystomella crispa and Polymor- 

 jphina oblonga on the Dorset coast, by plucking up 

 at random, from the verge of low water, tufts of 

 the common Coralline, of Rkytiphlea, &c, and 

 putting thern into a glass vase of sea-water. The 

 Foraminifera will crawl out and adhere to the 

 sides of the glass, where they must be searched 

 for with a lens. 



Identification. — The number and arrangement 

 of the chambers ; and the nature, form, position and 

 direction of the orifice, afford the chief grounds for 

 the sub-division of the group. 



Zoological Rank. — Considerable diversity of 

 opinion exists on this .point among naturalists. 



