INTRO U CG ErON 
DEFINITION AND SCOPE OF PALAEONTOLOGY 
Palaeontology (Adyos tév taaidv évrwv) is the science which treats of 
the life which has existed on the globe during former geological periods. It 
deals with all questions concerning the properties, classification, relationships, 
descent, conditions of existence, and the distribution in space and time of the 
ancient inhabitants of the earth, as well as with those theories of organic and 
cosmogonic evolution which result from such inquiries. 
By fossils, or petrifactions, are understood all remains or traces of plants 
and animals which have lived before the beginning of the present geological 
period, and have become preserved in the rocks. The evidence which is in 
all cases conclusive as to the fossil character of organic remains is the 
geological age of the formation in which they occur, whereas their mode and 
state of preservation, or the fact of their belonging to extinct or to still living 
species, are merely incidental considerations. Although, as a rule, fossils have 
undergone more or less radical changes during the process of fossilisation, and 
are usually converted into mineral substances, as the term petrifaction indi- 
cates, nevertheless, under exceptionally favourable conditions (as in frozen 
ground, amber, resin, peat, etc.), plants and animals may be preserved 
through geological periods in a practically unaltered state. Carcasses of 
mammoths and rhinoceroses entombed in the frozen mud-cliffs of Siberia, and 
inclusions of insects, spiders, and plants, in amber are none the less genuine 
fossils, in spite of their having sustained no trace whatever of mineral 
infiltration. 
A by no means inconsiderable number of plants and animals occurring 
strictly fossil in Tertiary and Pleistocene formations belong to still living 
species ; while, on the other hand, the remains of forms which have become 
extinct during historical times (2hytina, Alca, Didus, Pezophaps, ete.) can no 
more be classed as fossils in the true sense of the word than all such recent 
organisms as may chance to become buried in deposits now forming under the 
present prevailing orographic and climatal conditions. 
The changes which organic bodies undergo during the process of fossilisa- 
tion are partly chemical and partly mechanical in their nature.’ According 
1 White, Charles A., Conditions of preservation of invertebrate fossils, Bull. U.S. Geol. and 
Geog. Survey Territ., 1880, vol. V. p. 133. 
Trabucco, Giac., La Petrificazione. Pavia, 1887. 
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