314 THE FOEAMINIFEEA 



It is sometimes desired to arrange a group of 

 Foraminifera, or a series, upon a slide before mounting 

 in balsam. This can be eifected by washing the sur- 

 face of the slide with a thin layer of gum ; the objects 

 may then be placed in position, or arranged with the 

 aid of a moistened brush or a needle mounted in a 

 handle. The specimens can then be covered with 

 Canada balsam and mounted in the usual way. 



On Freparing Thin flections of the Tests of 

 Foraminifera. — The internal structure of the forami- 

 niferal test is revealed by means of thin sections cut 

 in various and definite directions. Sometimes only 

 one half-section is required, and if the specimen 

 be large, like a Nummulite or an Orbitoides, the 

 object may be held in a cork slightly hollowed at 

 the end, into which the specimen is pressed, and 

 rubbed on a snakestone or Water-of-Ayr stone with 

 water until one half of the specimen is entirely 

 removed by grinding. 



In the same way a polished specimen of a forami- 

 niferal limestone will show the included tests of 

 Foraminifera cut in various directions, and when 

 this surface is examined with a lens a great deal 

 may be learned about the internal structure of such 

 fossils. 



When a thin section of a shell measuring no 

 more than ^^^ inch in diameter, or even smaller, has 

 to be cut through the median plane, then the coarser 

 methods of cutting and polishing must be re- 

 linquished for the more delicate methods of Wallich, 

 Schlumberger, and others. 



