MICROSCOPIC FOSSILS. 



55 



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 

 Polythalamia,* or many chambered shells; termed the Rotalia,t or wheel- shaped 

 animal, and the curious Textularia,J or entwined animal. 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 per 

 fectly 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 Nummulites,! or fossil-money. Fig. 82. Fig. 83. Fig. 84. 



In figures 82 and 83 are delineated 

 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 original 

 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 assumes 

 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. 8T. 



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

 fossil, which occurs abundantly in the chalks of France, and is also found in those 



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



t From rola (Latin), a wheel. 



+ From textura (Latin), icoven-worlc. 



\ From foramen (Latin), opening, and/err (Latin), to bear. 



| Prom nummus (Latin), a coin, and lithos (Greek), a ston*. 



