198 TEREBELLA. 



The body extends about five inches ; and it is provided with about 

 seventy long and strong tentacula, stretching nine inches, which are 

 capable of sweeping an area eighteen in diameter around the head, while 

 the body remains stationary. 



Six branchiae are disposed in three pairs, the highest pair the longest, 

 the other two successively decreasing. These are fine and florid organs, 

 of peculiar formation, appearing somewhat mottled like birch bark un- 

 der the microscope. These parts are alike numerous as those of the 

 others, but they do not abound in similar curvatures, their extremities 

 terminate in forks like thorns. Their action is incessant, whence, toge- 

 ther with the slightest movement of the animal withdrawing them every 

 instant from the field of the microscope, excessive difficulty obstructs 

 the delineation of even a small portion magnified, Plate XXVI. fig. 8. 

 Thirteen transverse furrows indent the upper portion of the body, which 

 is subdivided into numerous annulations, and tapering down towards the 

 lower extremity. 



As the animal extends its body, the annulations of the upper por- 

 tion are quite obliterated. 



The whole is of a fine reddish-brown colour, the surface universally 

 speckled with low white tubercles, rendering it altogether a very beauti- 

 ful object. 



This Terebella constructs a wide loose case of fine sand, so large 

 that it can reverse itself within, and sometimes the tentacula are seen 

 protruding from both orifices. At first, from its general resemblance to 

 \he.figidus, I thought it might construct a tube of mud or clay. But it 

 testified no disposition to work in either, though employing some frag- 

 ments of comminuted shell along with the sand. Night is the season of 

 its greatest activity. 



When dislodged from the tube for the purpose of inspection or de- 

 lineation, and then supplied with sand, the higher portion of the body 

 is that which is first protected by the rudiments of a new edifice. 



The specimen represented Plate XXIX. fig. 1, having been com- 

 mitted to a wide vessel with a quantity of sand, it continued lurking 

 within at its work. Desirous of observing its future operations, I then 



