NORTHIA. 



139 



changes, for the remainder of the body is soft, with rather broader 

 rings, full of a glairy mucus, and of egg-like bodies that communicate 



No. XXI. 



a mottled appearance to it. The feet of these rings are slightly pro- 

 tuberant, and the bristles, although all simple, are of four sorts : 



1st, the spines ; 2ndly, some with a short curved sharp point (fig. e) ; 

 3rdly, others with a more elongated point (fig. b) ; and 4thly, two 

 with a strong shaft and a forcipate apex (fig. e). 



Between the two species of Northia there is a very exact resem- 

 blance in the form of the head and its various appendages, so that it 

 would be difficult to obtain in them a character by which they mio-ht 

 be distinguished. Northia conchyleya has seven jaws, exclusive of 

 the two pieces that constitute the under support ; and the jaws are 

 serrated with obtuse denticulations (fig./"). 



The tube of Northia conchylega is fully 3 inches long and ^ths 

 broad, flattened like the scabbard of a sword, open at both ends, 

 and constructed of fragments of old bivalve shells, of echini, and of 

 gravel rudely agglutinated together, and encasing the proper case of 

 the worm* : this is membranous, tough, and quite smooth. To 

 fabricate the tube, the creature has the ])roperty of secreting a large 

 quantity of a colourless glairy fluid, which is so tenacious that it 

 may be drawn out into threads a foot in length without breaking. 



(a) Berwick Bay, Dr. Johnston. 



(b) South Devon, J. Cranch. 



* It resembles the tube of Onuphis Eschrichtii of Oersted exactly (Grtenl. 

 Annul. Dorsibr. f. 45), but the two species are otherwise distinct. 



