UNIVALVES,.— TEREDO. 197 
TEREDO.—Suie-W orm. 
DESCRIPTION OF PLATE XXXV. 
Fig. 1. Section of the T. navalis, exhibiting its chambered structure. 
Fig. 2. Tubular valve of the same. 
Fig. 3. The animal which inhabits the tubular part, shewing the 
head and terminating valves affixed to it. 
=I 
a 
g. 4. A valve detached from the head, illustrating its interior form- 
ation. 
Fig. 5. Ditto, terminating valve. 
Fig. 6. A group of the T. navalis embedded in wood. 
Shell tapering, flecuous, and capable of penetrating wood. 
THERE are but four species of this genus at present 
discovered. 
The T. gigantea* is the largest species known, hav- 
ing been found exceeding five feet in length: it is 
nearly straight, and tapers towards one end, at which 
an interior tube is visible. It is a native of the Island 
of Sumatra, where it is found embedded in indurated 
mud. Some of the largest specimens seen in this coun- 
try are said to have been thrown up by an earthquake. 
The next species is the T. navalis, or common Ship- 
worm, a very thin, cylindrical, and smooth shell, varying 
in length from four to eight inches; it is generally a 
little twisted, and rather obtuse or blunt at the tip. It 
has the faculty of penetrating the stoutest oaken planks 
of ships’ sides, by means of two valves affixed to the 
* Sir E. Home has written a very scientific and interesting 
description of this singular shell.—See Phil. Tran. Feb. 13, 1806. 
