BIVAL VES. 
417 
a delicacy, and many species are highly phosporescent. In the second family the 
ship-worm ( Teredo ) is only too well-known on account of the amount of damage it 
does to submerged timber. It matters not whether it be oak, pine, teak, or 
mahogany which it attacks, soon the timber is riddled through and through, and 
rendered useless. In former times, before the invention 
of copper-sheathing, immense damage was inflicted upon 
shipping, and the piles of piers and harbours were con¬ 
stantly having to be renewed through the ravages of 
this pest. The Dutch have been great sufferers, and 
at one time such depredations had been made on the 
piles which support the dykes of Zealand and Friesland 
as to threaten them with total destruction. The animal 
is practically nothing more than an extremely prolonged 
Pholas. The siphons are of immense length, in some 
cases from two to three feet long, united except towards 
the ends. On the contrary, the body itself containing 
the principal viscera is small, and protected by a 
globular, bivalved shell, open both in front and behind. 
The gills are narrow, elongate, and prolonged into the 
branchial siphon. The siphons secrete a shelly lining 
to the burrow, and at the point where they separate 
there are a pair of calcareous plates, or pallets as they 
are termed, probably used as a means of defence, in 
closing the tube after the siphons have been retracted. 
Ship-worms generally bore with the grain, only turning 
aside to avoid a knot or any other obstruction; and 
although their burrows are almost touching, they 
seldom appear to run into one another. The animal 
does not feed upon the wood it excavates, but ejects it 
in small particles through the siphon. The foot is 
probably the burrowing organ, but the method of 
excavation is still imperfectly understood. Hyperotus, 
Nausitoria, Xylotrya, and Gyphus are other forms of 
Teredinidai ; the last named constructing a strong, 
shelly tube, sometimes a yard long, and two inches in 
diameter, in which the creature lives buried in the sand. 
Suborder Anatinacea. 
ship-worm ( Teredo) and its larva. 
This, the last suborder of the Eulamellibranchiata, 
contains thirteen families of which only a few are of 
general interest. Of the Pandoridce, the typical Pan¬ 
dora is distinguished by its compressed, internally pearly shell, which is sometimes 
semi-lunate in form; the right valve being flat, and the left somewhat convex. 
P. inoequivalvis is a common British species. In Myadora, an allied genus, the 
left valve is flat, and the right convex. The species of the third genus, Myochama, 
vol. vi .—27 
