12 



PART I. GENERAL ACCOUNT 



The cephalic lobe only rarely looks like a simple prolongation of the 

 protosoma, narrowing to the tip {Siboglinum weberi; S. caulleryi, Fig. 3; 

 S. pellucidum, Fig. 20). Usually it is rather sharply differentiated, and in some 



—tc 



Fig. 5. Front end of the body of a female Spirobrachia grandis from the right side. 

 с - cephalic lobe; со - dorsal ciliated band;/- keel of the bridle; mts - metasoma; p -adhesive 

 plaques; pa - adhesive papillae; ps + ms - the fore-part of the body formed by fusion of the 

 protosoma and the mesosoma; sv - ventral sulcus between the rows of adhesive papillae; 

 tc - tentacular crown ; te - outermost tentacle. 



forms (S.fedotovi, Fig. 6; S. plumosum and other species of this genus; and 

 also in Polybrachia and Galathealinum) it is delimited from the protosoma by 

 a pretentacular groove. The cephalic lobe is usually conical or triangular and 

 not infrequently dorso-ventrally flattened. 



