UNIVALVES, —SABELLA. 139 



TERE DO.^Ship- Worm. 



♦Navalis — Common. Utriculus — Timber. 



Clava — Club-shaped. 



SABELLA.— Sabella. 



Animal — a Nereis, with a ringent mouth, and two thicker 

 tentacula behind the head: Shell tubular, composed of 

 particles of sand, broken shells, and vegetable substances, 

 united to a membrane by a glutinous cement. 



This very extraordinary genus contains no less than 

 twenty-five species. The membrane which composes 

 the basis of these animals, is covered with various frag- 

 ments and particles of different marine and vegetable pro- 

 ductions. 



The S. vegetabilisand S. arundinacea are covered with 

 fragments of twigs, the bark of stems, or reeds, and brok- 

 en pieces of tellina cornea. The S.ammoniata is coated 

 with fragments of the cornu ammonis. 



The covering of the S. Indica is composed of capillary 

 sub-cylindrical agglutinated crystals of quartz; and that 

 of the S. clavata of various sized stones. 



Some of the species, as the S. scruposa, S. chrysodon, 

 &c. are detached, whereas the S.scabra is affixed by the 

 base. 



The S. alveolata has numerous parallel tubes, comnm- 

 nicating by an aperture, forming in the mass the appear- 



