POLYCH^ETA UF THE L.M.B.C. DISTRICT. 143 



To facilitate future reference, a figure is given of the 

 brancliia pertaining to the 21st setigerous somite. (PI. 

 XIII, fig. 10). 



*OnHphis (Northla) co/ichilega, Sars. 



Great numbers of this widely distributed worm were 

 taken on the " Spindrift " cruise (September '27th, 1890), 

 25 miles N.W. of Liverpool Bar — depth, 21 fathoms — for 

 the first time in this district. The animals are very 

 irritable w4ien expelled from their homes ; breaking into 

 fragments at once. The anterior part of the body is firm; 

 the middle and posterior soft and indefinite. The scabbard 

 shaped tubes which 0. conchilega constructs bears some 

 analogy to the stick or stone encrusted tubes of the larvae 

 of the caddis-fly. Like the latter, they are unattached to 

 any fixed object and can be dragged from place to place 

 by their owners, who can turn themselves if they please 

 in the tube. All sorts of shell fragments and bits of 

 echinid tests are requisitioned and fitted into place. When 

 we remember the diversity in shape and size of the material 

 and that wiien completed neither are the edges of adjoining 

 fragments allowed to overlap, nor are any unarmoured 

 spaces left in the tough membranous tissue forming the 

 framew^ork of the tube w^e must concede a considerable 

 amount of ingenuity and skill to Onupliis conchilega. 

 Such a tube is protective both by reason of its strength 

 and great relative size as compared with the worm itself 

 and also on account of the admirable way in which it 

 assimilates to the general appearance of the sea-bottom 

 w4iere it is found. 



M'Intosh in the " Challenger" Eeport (where he uses 

 the form Nothria for Northia as the name of this geims) 

 says — "The Onuphididae are distinguished from the Euni- 

 cida3 by their bathymetrical distribution for wiiile the 

 latter are often found between tide-marks, the Onuphididse 



