NO. 4 FORAMINIFERA — CUSHMAN I3 



gum arabic and water with enough glycerine added to prevent crack- 

 ing. The moistened brush will soften this enough so that the specimen 

 will be firmly fixed to the surface. If necessary it can be removed very 

 quickly by again moistening the gum below the specimen with the 

 brush. Specimens in this way can be mounted in any position for 

 drawing or photographing, or to show any detail of structure. 



Slides are procurable which have a large surface divided into as 

 many as 100 numbered spaces. These may be used for the different 

 species of a single locality but are not elastic if a collection is to be 

 arranged in any systematic way. In the earlier collections of the U. S. 

 National Museum wooden sHdes, devised by Dr. Flint, were used. 

 These were of two different sizes. The specimens were either attached 

 to the bottom of the cavity or were left loose. • They were then 

 covered with a square of mica, which was held in place by brass 

 clips. These slides, however, are difficult to arrange well on account 

 of the clips, and if these become loosened the contents may easily 

 be lost, the pasteboard slides being much more satisfactory for 

 general use. 



In warm countries it has been found that the ordinary concave glass 

 slide can be used to advantage, the specimens placed in these and a 

 glass cover placed over them. This may be held in place in various 

 ways. The disadvantage of this type of mounting is that specimens 

 become lodged in the narrow space at the edge of the cell and the 

 slides, themselves, are easily broken. If the pasteboard slides are 

 made of reasonably heavy material and paste instead of glue used 

 they will be found serviceable under almost any conditions. 



Needles are sometimes used for picking out specimens, but they are 

 not elastic, do not retain moisture and are much less satisfactory than 

 the very fine sable brush already referred to. Camel's hair brushes 

 are not sufficiently elastic to be of much service. 



FOSSIL MATERIAL 



Where fossil material can be washed as in the case of many clays, 

 sands and marls, they can be treated exactly as recent material. 

 Where the material has become consolidated into hard limestones 

 very often the only method of studying the contained foraminifera 

 is through thin sections. These may be prepared in the same manner 

 as ordinary rock sections. The study of such sections has decided 

 limitations. They show for the most part the outline in one plane and 

 something of the details of the internal structure. As most foraminif- 

 era are determined specifically by their external characters it is next 



