12 INTRODUCTION. 



Terehella.— Body oblong, creeping, naked, furnished 

 with lateral fasciculi or tufts, and branchiae; mouth pla- 

 ced before, furnished with lips, without teeth, and pro- 

 truding a clavated proboscis; feelers numerous, ciliated, 

 capillary, and placed round the mouth — This animal is 

 an inhabitant of many species of Dentalium, Serpula, 

 and Sabella. 



Nereis. — Body long, creeping, with numerous lateral 

 peduncles or feet on each side ; feelers simple, rarely none ; 

 eyes two or four, rarely none. — According to some natu- 

 ralists, the Nereis inhabits some species of Sabella. 



Clio. — Body oblong, natant, generally sheathed, and 

 furnished with two dilated membranaceous arms or wing- 

 like processes; tentacula three, besides two in the mouth. 

 According to some naturalists, it is an animal belonging 

 to this genus, which inhabits the Argonauta. 



