54 



THREE CRUISES OF THE " BLAKE. 





in the tubes, such marked peculiarities may occur in their choice 

 and application that from a fragment of the tube the builder 

 can be inferred with certainty, and the form of 

 the tubes (Figs. 261, 262, 

 263) may even be so char- 

 acteristic that there is no 

 danger of mistaking them 

 for other tubes. We have 

 examples of this kind 

 especially in the Eunicidae, 

 and also in the Maldanidae 

 (Fig. 264), Terebellidse, Sa- 

 bellidae, and Serpulidae. In 

 determining the distribution 

 of the worms, it must be 

 remembered that uninhab- 

 ited tubes, usually filled by 

 mud or other material from the bottom, may be transported by 

 currents. 



Many of the principal types of the littoral annelids have not 



Fig. 264. Maldane 



Fig. 205. Cirra- 

 tulus melaiiacan- 

 thus. -?. 



Fig. 260. Amphinome Pallasii. f . 



been dredged beyond the hundred-fathom line; such familiar 

 groups as the Syllidae, Nereidse, Cirratulidse (Fig. 265), and 



Amphinomidse (Fig. 266), have no 

 representatives at that depth, while 

 the Phyllodoeidse, Ariciidae, Tere- 

 bellidse, and Sabellidae extend to 

 300 fathoms, and such families as 

 the PolynoidaB (Fig. 267), Eunicidae, 



J 



Ophemdse, Aphroditidae, and berpu- 

 lidae live beyond the five-hundred-fathom line, where occur 

 also the Ampharetidse, many of which live in tubes lined with 

 a chitinous layer. 



Fig. 267.- Sthenelais simplex. 



