178 Proceedings of the Biological Society of Washington. 



on every other segment on a side and alternately with those of the op- 

 posite side; farther caudad two and three or more segments come to inter- 

 vene between the successive branchiferous ones, the number intervening 

 in posterior region becoming very large. Branchiae assuming a high 

 dorsal position in going caudad as usual. On the segment preceding 

 the first setigerous one occurs also two slender tentacular cirri, one 

 arising on each side from caudal edge of segment in front of branchiae of 

 succeeding segment; these tentacular cirri filiform, much more slender and 

 shorter than the typical branchiae, each reaching to near anterior end 

 of prostomium in the type, but in one paratype much longer. Special 

 branchiae of principal groups commonly strongly coiled, the longest bran- 

 chiae 25 and 30 mm. long. Neuropodia and notopodia widely separated. 

 Crochets of neuropodia stout and black, first occurring on or adjacent to 

 the nineteenth setigerous segment, mostly three or two but sometimes four 

 in each series. Body dark brown with a bluish black pigment tinging 

 anterior end of body; series of dark spots along each side, one spot present 

 at base of each neuropodium and notopodium. The special branchiae 

 of the principal group typically also colored with this dark pigment except 

 proximally, sometimes annulated, contrasting strongly with the other 

 branchiae which are yellow. 



Number of segments near two hundred and eighty. 



Length up to 210 mm.; greatest width, 6 mm. 



26. Ambo convergens, sp. nov. 



Dark colored like perbranchiata , but the bluish black pigment diffused 

 over entire body, making this in general a notably deeper color; a deep 

 blackish longitudinal stripe just mesad of bases of neuropodia. Some of 

 branchiae, particularly those of principal special groups, dark beyond 

 proximal yellow region, the other branchiae mostly yellow. Principal 

 groups of special branchiae on the seventh setigeous segment, the group on 

 each side tending at ectal end to encroach on the preceding segment; 

 about twenty-five branchiae in each group, the groups well separated by 

 a middorsal naked area. On segments in front of this the number of bran- 

 chiae additional to the ordinary one on each side from one to three, on 

 segments caudad of the seventh setigerous mostly, but one additional and 

 only single branchiae occur caudad of about the twenty-ninth setigerous 

 segment. Branchiae caudad of this region few, mostly widely separated 

 with numerous segments between successive ones. Neuropodial crochets 

 stout and black, first appearing in the twentieth setigerous segment on 

 which and about forty following ones they number two, or very rarely 

 three, on each side, and thereafter but a single one occuring in each neuro- 

 podium. 



Number of segments near two hundred and sixty-five, these very short 

 and closely crowded. 



Length, 75 mm.; greatest width, 6 mm. 



