3 
449 THE MEDALS OF CREATION. Cuar. XI. 
of each should be preserved. Mastic varnish, or solution of — 
gum tragacanth, delicately applied to fragile shells, tends to — 
preserve them, and improves their appearance. It is de- : 
sirable to collect the same species in various states of growth; — 
the form of the young shell (as in Rostellaria ampla, of 
Solander) often differing essentially from that of the adult. 
It will be found convenient to have trays or boards of — 
different colours ; and to select one tint for the shells col- 
lected from a particular formation, or deposit ; for example, 
the newer Tertiary may be placed on yellow paper; the 
older, or Eocene fossils, on light-blue. It is also desirable 
to separate the marine from the fresh-water species. 
Shells imbedded in chalk, limestone, &c., often require 
much labour to display their more delicate and important 
characters. For clearing chalk specimens, a stout penknife, 
and a few gravers or gouges of various sizes, will be neces- 
sary ; and by a little practice, the spines of the Spondylus © 
(Lign. 128), and the beaks and hinge of Inocerami (Lign. 
129), &c., may be readily exposed. A small stiffish brush, 
used with water, is also serviceable. The shells in compact 
stone, as those of the mountain limestone, must generally be 
cleared with the hammer and chisel. Common species may 
be broken out, and, from several examples, probably one or 
two will be found perfect ; but choice and rare specimens 
should not be thus risked ; they will amply repay the trouble 
of the less expeditious method of chiselling away the sur- 
rounding stone. Casts may be taken in gutta percha, &e. 
To determine the names of the specimens that he has 
collected should be the next care of the student. No 
method will so readily initiate the young collector in fossil 
conchology, as the careful examination of a small series of 
the common species, with their names attached.* By the | 
* Such a series may be obtained, at very little cost, of dealers in 
objects of natural history ; as, Messrs. Tennant, Sowerby, the British 
Natural History Society, &c. See Appendix. 
