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PART II. SYSTEMATIC ACCOUNT 



is thin, but thickens a little in the middle. Its length to breadth ratio is 8 or 

 9:1, but in one individual, which had an extended fore-part, it was no 

 less than 18 : 1 (Fig. PP133). The protosoma is limited behind by a distinct 

 annular groove, lying a short distance in front of the bridle. Towards the 

 front end the protosoma tapers imperceptibly and runs into the small 



Fig. QQ133. Siboglinum exile: A - the fore-part of the body from the ventral, B, from the dorsal, 

 and C, from the left side; D - part of the tentacle. 



с - cephalic lobe : ci - glandular girdle ; f- bridle ; gt - flask-shaped gland ; pa - papillae ; pi - pin- 

 nules ; s 1 - groove between the protosoma and mesosoma ; s 2 - groove between the mesosoma and 

 metasoma; sv - ventral sulcus; t - tentacle. 



