KEY FOR IDENTIFICATION FROM TUBES 459 



rings equals the diameter of the tube, which may be more than 

 0-2 mm. Siboglinum weberi (p. 181). 



45 (44) The rings have uneven edges. Between the elements of the fused 



double rings are retained only sparse, irregular clear areas. The 

 length of the secondary rings is no more than one quarter the 

 diameter of the tube which is 0-6 mm. 



Siboglinum plumosum (p. 197). 



46 (42) The rings are simple for the whole length of the tube. 



47 (60) The rings are regular, with equal front and back edges. 



48 (59) The diameter of the tube is not more than 0-5 mm. 



49 (54) The diameter of the tube is not more than 0-15 mm. 



50 (51) The rings are transparent, colourless or yellowish, with a glittering 



surface. The length of the rings is just a little more than half the 

 diameter of the tube. The tube is very soft and thin-walled. 



Siboglinum pellucidum (p. 233). 



51 (50) The rings are muddy-brown or yellowish brown and more or less 



opaque. 



52 (53) The rings are equal in length, each one about half the diameter of 



the tube. Siboglinum buccelliferum (p. 224). 



53 (52) The rings vary in length, but are never longer than the diameter of 



the tube. Diplobrachia belajevi (p. 376). 



54 (49) The diameter of the tube lies between 0-2 and 0-5 mm. 



55 (58) The diameter of the tube lies between 0-2 and 0-3 mm. 



56 (57) The rings are dark brown, almost black, and about half to two 



thirds the diameter of the tube in length. 



Siboglinum caulleryi (p. 216). 



57 (56) The rings are brownish or almost colourless, and almost equal in 



length to the diameter of the tube, but in part they may diverge to 

 one side or other of this length. In the hind part of the tube the 

 rings are only half to two thirds as long as the diameter of the tube. 



Siboglinum norvegicum (p. 251). 



58 (55) The diameter of the tube is up to 0-45 mm. The rings are golden 



brown and their length is one third to a half the diameter of the 

 tube. Heptabrachia beringensis (p. 347). 



59 (48) The diameter of the tube lies between 0-5 and 0-7 mm. The rings 



are muddy-brown, some of them with darker edges. 



Oligobrachia dogieli (p. 155). 



60 (47) The rings are irregular with uneven edges. 



