[387] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 93 
to a very large size in one season, it is evident that the best time to 
take up the buoys would be in midsummer, before the early crop of 
young have grown large, and leaving too little time for the later crop 
to become large, in the buoys thus put down, before winter, when most 
of them would probably be killed by the cold weather. In this way 
the damage might be materially diminished, if not inconsistent with 
the other duties of the officers of the vessels employed in this service. 
There are, as yet, no means of estimating the extent of the damage 
done to our wharves, shipping, &e., by this and the various other species 
of Teredo found on our coast, but judging from their abundance along 
the whole coast, it is much greater than is generally supposed. 
The Teredo navalis is also abundant on the coast of Europe, from the 
hs and Black Seas to Christiania, and the coasts of Great 
Brifain. Its habits have been quite thoroughly investigated by several 
Dutch naturalists, owing to the great damage that it has done on their 
coast, at times even threatening a general inundation of the country by 
destroying the wood-work of the dikes. This Teredo occupies a zone 
of considerable breadth, for it often lives considerably above low-water 
mark and extends several feet below it, even to the depth of fourteen 
feet, according to some writers. 
The best remedies in common use to resist or prevent its attacks are 
copper-sheathing, used chiefly on vessels; broad-headed nails, closely 
driven, used for piles and timbers; creosote and coal-tar, frequently applied. 
The various poisonous substances that have been applied to timber for 
this purpose. however useful they may be in other respects, have little 
or no effect on the Teredo, for it does not depend upon the wood for its 
food, and even protects its body externally with a layer of shell, lining 
its holes. The only remedies that are likely to succeed are those calcu- 
lated to prevent the lodgment and entrance of the young ones beneath 
the surface. Even creosote, thoroughly applied under pressure at the 
rate of 10 pounds per square foot, has been found insufficient to prevent 
their attacks, for piles thus treated at Christiania were found by Mr, 
Jeffreys to be filled with the Teredo within two years after they were put 
down. 
Several other species of Teredo also occur on this coast. The Teredo 
megotara (Plate XX VIT, fig. 188) has been found in floating pine wood at 
Newport, Rhode Island, and in cedar buoys, &c., at New Bedford, 
Massachusetts; as well as in Massachusetts Bay, at Provincetown and 
other places; it is also found as far south as South Carolina at least. 
This species sometimes grows toa large size, forming tubes at least 
eighteen inches long. It sometimes occurs, also, in the piles of wharves 
in this region. The Teredo Thomsoni (Plate XXVII, fig. 187) has been 
found in great numbers in the marine railway and also in cedar buoys 
at New Bedford. It has also been found at Provincetown in a whaling- 
ship that had cruised in the West Indies. 
The Xylotrya fimbriata (Plate XX VII, fig. 189) is very similar to the 
