90 REPORT ON COMMISSIONER OF FISH AND FISHERIES. [384] 
the young ZVeredos but they gradually grow larger as they go deeper and 
deeper into the wood, until they sometimes become ten inches or more 
in Jength and a quarter of an inch in diameter, but the size is generally 
not more than half these dimensions. The holes penetrate the wood 
at first perpendicularly or obliquely, but if they enter the side of the 
timbers or planks across the grain, the burrows generally turn horizon- 
tally in the direction of the grain a short distance beneath the surface, 
unless prevented by some obstruction, or by the presence of other 
Teredo tubes, for they never cross the tubes of their companions or 
interfere with each other in any way, and there is always a thin layer 
or partition of wood left between the adjacent tubes. It is, however, 
not necessary that they should follow the grain of the wood, for they 
can and do penetrate it in every direction, and sometimes not more 
than half the tubes run in the direction of the grain, and they are often 
very crooked or even tortuous. They rapidly form their burrows in all 
kinds of our native woods, from the softest pine to the hardest oak, and 
although they usually turn aside and go around hard knots, they are 
also able to penetrate through even the hardest knots in oak and other 
hard woods. The Teredos grow very rapidly, apparently attaining 
maturity in one season, and therefore, when abundant, they may 
greatly damage or completely destroy small timber in the course of four 
or five months, and even the largest piles may be destroyed by them in 
the course of two or three years. 
The most abundant species in this region is the Teredo navalis (cuts 
land 2; Plate XXVI, fig. 183, animal; Plate XX VII, fig. 186, shell.) 
EXPLANATION OF THE CUTS. 
Fig. 1. Posterior or outer end of a living Teredo navalis, removed from its burrow ; 
c, the muscular collar by which it adheres to the shelly lining of its burrow ; p, the 
shelly “pallets” which close the aperture when the animal withdraws; ¢t, the two 
retractile siphon-tubes which project from the hole when the animal is active. 
Fig. 2. Anterior end and shell of the same; s, the front part of the shell; f, the 
foot or boring organ. 
This is the same species that has attracted so much attention in 
Europe, during nearly two centuries, on account of the great damage that 
it has done, especially on the coast of Holland. Nevertheless no fuil 
description of the animal of this species has yet been published, nor 
any satisfactory figures of the soft parts. 
When removed from its tube (see Plate XX VI, fig. 183) the animal is 
