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AND PRESERVING FOSSILS. 
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Such slaty rocks, though apparently barren, may prove (like the 
Welsh Cambrian rocks) to be very fossiliferous, if the organic 
remains are sought for on the edges of slabs, sometimes at right 
angles to the cleavage planes. 
2. Even when limestones appear to be unfossiliferous, it is well 
to examine them — and especially the cherty bands and nodules so 
frequent in them — with a good hand-lens to detect microscopic 
organisms. Shells of Eoraminifera and Radiolaria, spicules of 
Sponges, etc., may frequently be detected by a lens on smooth, 
wetted surfaces. 
3. Similarly, apparently unfossiliferous clays are not to be 
neglected. Samples may be taken and " washed " at home, the 
result being frequently abundant remains of Foraminifera and 
Ostracoda, etc., from marine deposits, and seeds of plants from 
comparatively modern fresh-water deposits. 
4. When a formation contains nodules or concretions, special 
attention ought to be paid to these. They have usually been 
formed around decaying organic matter, and a large proportion of 
the best-preserved fossils occur in them. 
The clay-ironstone nodules found in the beds associated with 
seams of coal usually contain remains of coal plants, insects, and 
Crustacea enclosed within them, often of great beauty. 
Many concretions enclose fossil fishes. The late Mr. Charles 
Moore found, after long experience, that the nodules of White Lias, 
containing fishes, were most successfully opened by first breaking 
them in two near the centre, and then splitting open each half 
at the inner transverse fracture. The two halves of the split 
surfaces were afterwards glued together. 
Treatment of Fossils in the Field. 
1 . As a general rule, it is best to do the least possible trimming 
and cleaning of a fossil in the field. Final preparation for the 
cabinet can be far better done at leisure afterwards. 
2. Large friable specimens, such as vertebrate skeletons, large 
Ammonites, or groups of shells, in a matrix which is only moderately 
hard or liable to fall to pieces on drying, need special treatment. 
