Different borings in consolidated material.

A) natural empty mould in a flint concretion - Norwich, England.
B) natural boring cast. C) winding and branched boring in a Pliocene oyster - Puglia, Italy.
D) seed shaped borings in a limestone pebble, Pliocene - Puglia, Italy.
E) cluster of what is seen in picture D) with boring threads
(Donovan, 1994)