AND PRESERVING SHELLS. 
105 
surface is cleared. A file will often be useful, 
but it will require some skill to stop at the 
proper moment. When the rough coating is 
removed a rubber of leather glued on a piece 
of wood, dipped in fine powdered pumice di- 
luted with a little oil, should be used, and the 
last polish given with fine red ochre. The 
shells should then be cleansed with warm water, 
then dipped in alkali to neutralize the effects 
of the acids used, and finally washed in clean 
water ; and when wiped quite dry, may be 
covered with a weak solution of gum arabic. 
As to packing, all that is necessary is, after 
the shells have been completely cleansed and 
dried, to place them in bottles, jars, or boxes 
mixed with fine dry sand or sawdust, or wrap- 
ped in cotton, so that they may not rub each 
other. Those with spines will require particular 
attention. 
In arranging shells the best method with 
the smaller species is to have pieces of thin 
board, covered with white paper, of an uni- 
form size and thickness, on each of which the 
specimens should be gummed. The univalves 
should be placed with their mouths downwards, 
except one specimen of each species, which 
should be reversed. A series of varieties gra- 
dating from the two extremes of size would 
