POLYCH^TA OF THE FAMILIES SERPULID^ AND SABELLID^. 349 



The few specimens from Gough Island have less than thirty-two serrations to their 

 opercula, but it seems that they are quite young. 



Genus Apomatus Philippi, 1 844. 



Generic characteristics : — 



1. Operculum globular, terminating a gill retaining its pinnse. 



2. Some of the thoracic setse are bladed sickles (setae of Apomatus). 



3. Terminal dorsal gland present. 



Apomatus hroivnii n. sp. 

 Specific characteristics : — 



1 . Collar-setse with small fin at base of blade ; fig. 2, a. 



2. Uncini begin on the second thoracic segment, and have only seven or eight 



teeth ; fig. 2, d and e. 



3. Abdominal setse sickle-shaped ; fig. 2, c. 



Five specimens, more or less incomplete, from Station 417, lat. 71° 22' S., long. 

 16° 34' W., trawled at a depth of 1410 fathoms, 18th March 1904. 



This form differs from all other previously described species of the genus in the 

 characteristics 1 and 2 above, i.e. in the shape of the collar-setse and the uncini. 

 There is, however, complete agreement with the two main generic characteristics (1 and 

 2 above) as given by Saint- Joseph (16, p. 373). It is to be noted that this species 

 comes from very deep waters. 



Tubes almost cylindrical and smooth, except for inconspicuous growth lines. The 

 diameter of the oral aperture of the largest tube is 3*5 mm. ; 50 mm. from this is the 

 other aperture 175 mm., but this is probably not the real end of the tube, which 

 may have been attached to some substratum by a further narrower portion. Most 

 of the tubes have obviously been longer, but only one, the smallest, shows a scar of 

 attachment. 



The animals were preserved in their tubes. The total length of the longest is 

 27 mm., and of the shortest 16 mm. ; the greatest width is 2 mm. The fifteen pairs 

 of branchiae are spirally coiled. They measure from 6 to 10 mm. in length, and are thin, 

 with long fine pinnse extending almost to the tops of the rachises. 



One animal has its branchial crowns projecting from the tube, and has lost its 

 operculum. TVo others have lost their branchial crowns altogether. In the remaining 

 two, the second dorsal gill on the left or right terminates in a transparent globular 

 operculum. In one there is a secondary rudimentary operculum on the other side. 



The collar is L mm, deep, entire ventrally, but notched laterally, and very much 

 folded. There are only five or six collar-setse of the characteristic form, which, with 

 about half a dozen ordinary capillary setse with narrow blades, make only a small 

 fascicle. The other thoracic fascicles contain numerous setse, comprising ordinary 

 narrow blades and setse of the usual Apomatus type (fig. 2, h). 



