Index Fossil is the hardened remains or traces of plant or animal life from a previous geological period preserved in the Earth's crust.
(Index Fossil; is; the hardened remains or traces of plant or animal life from a previous geological period) (a previous geological period; preserved; L:in the Earth's crust)
Index Fossil a previous geological period
is preserved
the hardened remains or traces of plant or animal life from a previous geological period
L:in the Earth's crust