FOSSIL BONES. 45 
The permeation of the teeth by mineral matter, produces 
beautiful examples of the tissues of those organs; the 
dentine is often stained throughout with a rich sienna tint, 
and sections viewed under the microscope by transmitted 
light, reveal the character and distribution of the calcigerous 
tubes more clearly even than in recent specimens. 
It is extremely rare that osseous structures are found 
petrified by flint; among the many thousands of bones 
which I have extracted from the rocks, or have seen in col- 
lections, I know but of one instance of a silicified vertebra, 
that of a Mosasaurus, from a chalk-pit near Brighton ; and 
a few bones and scales of fishes. But notwithstanding the 
weight and apparent solidity imparted by these modes of 
mineralization, the substance is generally rendered extremely 
brittle, so that the development of the bones from the stone 
in which they are imbedded, and the removal of the hard 
ferrugino-calcareous crust investing them, is no easy task, 
_ but requires much tact, experience, and patience, to execute 
successfully. 
HINTS FOR COLLECTING FOSSIL BONES.—The light, friable, 
porous bones, require great care in their removal from the 
deposit in which they are imbedded, whether it be clay, 
consolidated shingle, or limestone ; if of considerable size, 
they will almost invariably break to pieces, and many 
examples will not admit of repair. Itis therefore always 
desirable, before attempting to extract a large bone, to 
make a sketch of it ; its form will thus be known, should it 
_ be destroyed ; and if it crack into fragments that will admit 
of reunion, the drawing will be a valuable guide for the 
replacement of the separated parts. If only a few pieces 
remain, those which show any portion of the terminations, 
or joints, should be preserved, as they afford the most 
precise and important characters. The faithful record even 
of an imperfect and unknown fossil is not without value ; 
and as the antiquary carefully preserves shreds of ancient 
