Portions most liable to destruction, those parts between the tide marks, were found perfectly sound, and showed no signs of the ravages of marine organisms. Other valuable timber trees of the eastern portion of the continent are the blackbutt, tallow-wood, spotted gum, red gum, mahogany, and blue gum, eucalyptus; and the turpentine (Syncarpialaurifolia), which has proved to be more resistant to the attacks of teredo than any other timber and is largely used in wharf construction in infested waters.
Jarrah timber is nearly impervious to the attacks of the teredo, and there is good evidence to show that, exposed to wear and weather, or placed under the soil, or used as submarine piles, the wood remained intact after nearly fifty years' trial.
Teredo navalis, it has been found necessary, for depths not exceeding 300 fathoms, to protect the core with a thin layer of brass tape.
Black ironwood is likewise used in building wagons, while sneezewood is largely utilized for supports for piers and other marine structures, being impervious to the attacks of the Teredo navalis.
(d) Univalvia absque spira regulari: Patella, Dentalium, Serpula, Teredo, Sabella.
In Teredo a similar tube is formed as the animal elongates (boring in wood), the original shell-valves not adhering to it but remaining movable and provided with a special muscular apparatus in place of a ligament.
When it is remembered that the woodwork is infested by the pile worm (Teredo navalis), the ravages of which were discovered in 1731, the labour and expense incurred in the construction and maintenance of the sea dikes now existing may be imagined.