UNIVALVES TEREDO. 197 



TEREDO Ship-Worm. 



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 auimal which inhabits the tubular part, shewing the 

 head and terminating valves affixed to it. 



Fig. 4. A valve detached iirom the head, illustrating its interior form- 

 ation. 



Fig. 5. Ditto, terminating valve. 



Fig. 6. A group of the T. navalis embedded in wood. 



Shell tapei'iny, Jiexuous, and capable of penetrating wood. 



THERE are but four species of this g-enus at present 

 discovered. 



The T. g-igantea* is the largest species knov, n, hav- 

 ing- been found exceedino- five feet in lenoth: 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. 



