270 THE MICROSCOPE. 



Stichostegidce ; that is to say, the chambers are also arranged 

 in a spiral form, but in a double series. A fifth family 

 includes those shells in which the chambers are arranged 

 round a common perpendicular axis in such a manner that 

 each chamber occupies the entire length of the shell. The 

 orifices of the chambers are placed alternately at each end 

 of the shell, and are furnished with a curious tooth-like 

 process. The Miliola serve as an example of this family. 

 Every handful of sea-sand, every shaking of a dried sponge, 

 and the contents of the stomachs of most Lamellibranch 

 molluscs, oyster and mussel, are pretty sure to exhibit a 

 considerable admixture of these minute calcareous, or 

 occasionally silicious, Foraminifera. 



It is considered that the fossil shells, termed Num- 

 mulites, found in great quantities in the chalk and lower 

 tertiary strata, are also to be regarded as members of this 

 class ; in a fossilized state, whole mountains consist almost 

 entirely of their shells. Professor Quekett has had an 

 opportunity of examining living specimens, which, he says, 

 " are composed of a sarcode element, built up into a series 

 of chambers with calcareous material." 



The great Pyramid of Egypt, covering eleven acres of 

 ground, is based on blocks of limestone consisting of 

 Foraminifera, Nummulites, or stone coin, and other fossil 

 animalcules. Nummulites vary in size from a very minute 

 object to that of a crown-piece, and many appear like a 

 snake coiled up in a round form. A chain of moun- 

 tains in the United States, 300 feet high, seems wholly 

 formed of one kind of these fossil-shells. The crystalline 

 marble of the Pyrenees, and the limestone ranges at 

 the head of the Adriatic gulf, are composed of small 

 Nummulites. Vast deposits of Foraminifera have been 

 traced in Egypt and the Holy Land, on the shores of 

 the Red Sea, Arabia, and Hindostan, and, in fact, may be 

 said to spread over thousands of square miles from the 

 Pyrenees to the Himalayas. 



The fossilized Foraminifera in the Poorbaudar lime- 

 stone, although occasionally reaching the twenty-fifth, do 

 not average more than the hundredth part of an inch in 

 diameter ; so that more than a million of them may be 

 computed to exist in a cubic inch of the stone. They may 



