138 UNIVALVES. TEREDO. 



*Retiex3L— Reflected. *L&ctea— Milky. 



•Cornea — Hortty. *Lagena — Oil flask. 



♦Bicornis — Semilunar. *Retorta — Retort-shaped. 



•Perforata — Perforated. *Incurvata — Incurved. 



TEREDO.— Ship-Worm. 



Animal — a Terebella, with two calcareous hemispherical 

 valves cut off before, and two lanceolate ones : Shell ta- 

 pering, Jlexuous, and capable of penetrating wood. 



There are but three species of this genus: the first is the 

 T. navahs, or common ship-worm ; it is very thin, cylin- 

 drical, and smooth, and is more or less twisted, and rather 

 obtuse or blunt at the tip; it varies in length from four to 

 six inches. This worm was originally imported from In- 

 dia, it has the faculty of penetrating the stoutest oaken 

 planks of ships' sides 3 and effects as much destruction in 

 the water, as the ternies or white ant on land. 



The T. utiiculus is also cylindrical, undulate, and so- 

 lid ; it is found in wood that has lain some time under 

 water. It is white, subpellucid, very much bent, and 

 gradually tapering, with an oval aperture, divided in the 

 middle by a partition. Its length is about seven inches. 



The third species is the T. clava, which is found in the 

 seminal vessels of the xilosteum granatumj one end is 

 clavate, the other incurved, narrower, obtuse, and perfo- 

 rated in the middle: the shell is rough, and brownish on 

 the Qutside, but within it is smooth, and more or less 

 flexuous. !t is nearly two inches long, but not half an 

 inch wide. 



