228 Journal of Applied Microscopy. 



Notes on Preparing Foraminiferal Material for Study. 



In the unconsolidated deposits of cretaceous and more recent age, foramini- 

 fera may be looked for in the marls, bryozoan deposits, calcareous sands, or 

 fine sands and clays. The coarse sands contain few or none, while the finer 

 materials — the products of slower sedimentation — are often quite rich. The 

 filling within the shells of bivalves is often much richer than the matrix around 

 these fossils. 



The material to be examined should be thoroughly dried and all masses or 

 lumps broken up. If the material — as for example, the bryozoan sands — con- 

 tains some of the larger or longer forms, it may be searched at once. If, how- 

 ever, only the more rotund and smaller forms are present, any coarse shell frag- 

 ments or other large-sized material may be separated by sieving the material, 

 using a mesh large enough to let the foraminifera pass through. If this sieved 

 material contains a large proportion of exceedingly fine clay particles, these may 

 be gotten rid of in a similar way — by using a bolting cloth sieve that will let the 

 clay particles pass through but retain the material of about the size of the fora- 

 minifera — say all larger than 0.2 to 0.4 mm. 



This mechanical separation may, in material of some textures, be carried a 

 step further by placing the material in a paper and gently shaking it in such a 

 way as to keep it in a rather compact mass but vigorously enough to let the parti- 

 cles move freely among each other. There will be a tendency for the foramini- 

 fera and other of the lighter constituents to work their way to the surface and 

 concentrate there, as it were. 



A pocket magnifier with a power of say six to twelve diameters, and as large 

 and fiat a field as possible, is necessar)', aided by a pair of sharp eyes. After 

 finding a specimen it may be readily picked out by touching it with the sharp 

 point of a fine, well moistened camel's-hair brush, or with the moistened end of 

 a rather blunt needle, or of a sharpened match or toothpick. 



For studying, one must be able to turn the unmounted specimen into any 

 position while under the microscope. This may be readily accomplished by hold- 

 ing it slightly entangled in the hairs of a dry camel's-hair brush. For study in 

 certain positions, it may of course be simply laid on a glass slide. The external 

 surface may be studied to best advantage when perfectly dry. Permanent 

 mounts show the external characters well when strewn over a black surface, e. g., 

 asphalt. To protect from accidents the mount should be surrounded by a gutta 

 percha ring. When mounted in balsam with a cover-glass, the external char- 

 acter is seen with difficulty, while more or less of the internal structure, accord- 

 ing to the species studied, becomes visible. 



To make sections showing the internal structure, the smaller specimens may 

 be imbedded in hard balsam and ground down very carefully until the median, 

 or desired, section is reached. It may then be mounted section side up, or this 

 side may be cemented on a slide and the opposite side ground down also. For 

 larger individuals the grinding may be easily accomplished by holding the speci- 

 men under the ball of the finger and rubbing gently on a piece of smooth ground 



