306 THE AQUARIAN NATURALIST. 



In some respects this animal bears considerable 

 analogy to the Terebella. The body of the little 

 parasite is about nine lines in length, composed of 

 numerous segments, and tapering towards each ex- 

 tremity; it is bordered throughout with a row of 

 pencils, composed of three or four setae each. The 

 mouth is a cavity in the anterior extremity, some- 

 what behind which are eight round flexible tenta- 

 cular organs situated on the neck; these are sus- 

 ceptible of being flattened and folded longitudinally, 

 like the tentacula of the Terebella. Eight of these 

 tentacles would seem to form the complete appa- 

 ratus, and they are possibly developed in succession, 

 seeing that specimens two lines in length have only a 

 single pair. 



The special habitation of this creature is a cavity 

 adapted to its size, often situated in the thickest part 

 of the shell. The cavity is lined with silk, and therein 

 the tenant lurks, protruding its tentacula through a 

 circular aperture; these are always employed in 

 searching round the vicinity, like those of the Tere- 

 bellse proper. 



Although not dwelling in society, several of these 

 worms may often be found within narrow limits. At 

 least a dozen have been seen displaying their tenta- 

 cula from the surface of a single shell ; besides which 

 there were probably others of small dimensions ob- 

 scured by adventitious matter. 



