ORGANIC REMAINS. 
79 
plentiful ; shells are innumerable ; the crusts of lobsters and crabs, and 
the scales of fishes are scarce, but teeth and vertebrae of the latter are 
more abundant ; aquatic reptiles have left us their bones. Now all these 
were originally durable; they are all capable of conservation in our 
cabinets : but the softer animal substances once connected to them, 
have entirely disappeared. Even the ligament which is placed at the 
hinge of bivalves to open the shell, is most rarely preserved in a 
fossil condition. Considerations of this nature render it extremely pro- 
bable, that the process of mineralization, or (as it is commonly called) 
petrifaction, was slow and gradual. 
Another general remark must be made to prevent misconception. Fos- 
sils are at some places found perfect, at other places in fragments. Now 
they must have been enveloped in these conditions respectively. From 
carefully observing these appearances, we may form pretty clear notions 
as to the tranquillity or agitation of the fluid in which they were de- 
posited. In general, substances originally bound together by perishable 
ligaments are found in detached pieces, owing to the decay of those 
parts previous to their being enclosed in the rocks. Thus the shells of 
crabs and lobsters are commonly disintegrated, bivalves are often sepa- 
rated and vertebras and teeth of fishes scattered far asunder in the 
rock. Such instances as these occur daily in our streams and on the sea- 
coast, and, therefore, in former periods may have happened without any 
particular agitation of the waters. 
Some beds of shells, as the forest marble of the neighbourhood of 
Bath, appear to have been accumulated with violence and confusion : 
but generally the sharpness of their angles and perfection of their orna- 
ments lead to the conclusion that they were quietly entombed near the 
spots where they lived. * The vegetable fossils are, however, a remark- 
able exception to this, and, being almost always in fragments, seem to 
* Consult the Prefaces of Mr. Smith’s works. Strata identified by Organized Fossils, and Stra- 
tigraphical System of Organized Fossils; and Cuvier’s Theory of the Earth, for illustrations on this 
poiut. 
