FOSSIL INFUSORIA. 



the flinty shells of animalcules, mingled with the scales of fishes, zoophytes, and 

 the remains of numerous minute animals. The microscopic animal structures 

 that abound most in the chalk and flint of England are two kinds of Polythala- 

 inia,* or many-chambered shells ; termed the Rotalia,f or wheel-shaped animal- 

 cule, and the Textularia,J or entwined animalcule. With these are combined 

 vast numbers of minute shells, belonging to an extensive class of small animals, 

 which, on account of their being covered with pores, 'have received the name of 

 Foraminifera. 



The shells of the Foraminifera differ in their dimensions. Some of them are 

 perfectly microscopic, being invisible to the naked eye ; while others are of the 

 size and shape of a dollar ; and from their resemblance to a coin have received 

 the name of N"ummulites,|| or fossil-money. 



In figures 82 and 83 are delin- Fig. 82. Fig. 83. Fig. 84. 



eated two microscopic shells of the 

 Rotalia, each of which is seen to ( 

 consist of several compartments, like 

 that of the nautilus; though they are 

 distinct from the latter in their nature. 

 The specimens, from which the ori- 

 ginal drawings were taken, were discovered in the chalk and flint of Surrey. 

 Figure 84 represents a portion of a nautilus found in a piece of Irish flint; five 

 chambers of the shell are clearly seen, partially separated from each other. 

 The three figures here presented are all very highly magnified. 



A beautiful species of microscopic fossil, that is likewise found in chalk, is the 

 Crosier-like shell, which in its advanced state changes its original shape, and as- 

 sumes the graceful form shown in figure 85, which presents a side view of the 

 object. This fossil was found at Chichester, by Mr. Walter Mantell, and is here 

 shown as it appeared when magnified eight times. 



Fig. 85. 



Fig. 86. 



Fig. 87. 



Another kind of the microscopic many-chambered shells is the Fan-shaped an- 



* From polus, (Greek,) many, and thalamos, (Latin,) a chamber. 



f From rota, (Latin,) a wheel. 



\ From textura, (Latin,) woven-work. 



From foramen, (Latin,) opening, and ferre, (Latin,) to bear. 



\ From nummusy (Latin,) a coin, and lithos, (Greek,) a stone. 



