146 UNIVALVES. — TERE0O. 



Division II. — Detached. 



*Semilunum — Small-reed. Anguina — Servient. 



Incuvxatgi— Incurved. Muricata — Prickly. 



Cereolus — Bougie. Annularis — Ringed snake. 



Nebulosa — Clouded tawny. Retorta — Retort-shap'd. 



Lumbricalis — Cork-screw. Cornu-copise — Cornucopia. 



Arenaria — Sandy. Decussata — Decussated. 



Afra — Smooth- brown. Proboscidea — Proboscis. 



Volvox — Caterpillar. Protensa — Lengthened. 



Division III. — With radiated border and perforated disk. 

 Aquaria — Watering-pot. 



TEREDO.— Ship-worm. 



Animal — a Terehella, ivith two calcareous hemispherical 

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

 pering, flexuous, and capable of penetrating ivood. 



THERE are but four species of this genus : the first is 

 the T. navalis, or common ship worm ; it is very thin, cy- 

 lindrical, and smooth, and is more or less twisted, and ra-. 

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

 to six inches. This worm was originally imported from 

 India, it has the faculty of penetrating the stoutest oaken 

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

 the water as the termes'or white ant on land. 



The T. utriculus is also cylindrical, undulate, and solid; 

 it is found in wood that has lain some time under water. 

 It is white, subpellucid, very much bent, and gradually ta- 

 pering, 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 



