SYLLIDAE 



129 



Specific characters. A small species measuring about 12 mm. in length for be- 

 tween 50 and 60 chaetigers. In spirit there is no colour. The head (Fig. 21 fl) is broader 

 than long and rounded in front. There are two pairs of eyes. The tentacles, tentacular 

 cirri and the dorsal cirri throughout the body are all very similar in shape and size. 

 They are simple, subulate structures, somewhat thickened basally and tapering to a 

 point, and their size is about equal to half the breadth of the body. The ventral tentacular 

 cirri are a little smaller than the rest. 



The pharynx extends to about the 4th chaetiger and the proventriculus to the loth. 

 The pharyngeal tooth is anterior and the mouth of the pharynx is smooth and sur- 

 rounded by a circlet of 10 papillae. The feet (Fig. 21 b) are more or less triangular in 

 outline and supported by three acicula. The bristles are all bidentate and the end-pieces 

 have a characteristic aspect, for the denticulations show a great increase in size from 

 above downwards (Fig. 21c). The ventral cirri are small and conical and scarcely reach 

 to the end of the foot. There is a pair of pygidial cirri resembling the normal dorsal cirri. 



■2MM 



Fig. 21. Pionosyllis nutrix. 



a. Head from above. c. Bristle. 



b. Middle foot. d. Dorsal view. 



A number of these specimens carry developing eggs on their backs (Fig. 21 d), the 

 embryos being arranged in pairs, one pair to each segment. 



Remarks. This species is at once separable from the other southern members of the 

 genus, P. comosa, Gravier, P. maxima, mihi, and P. stylifera, Ehlers, by the structure of 

 the dorsal cirri and the bristles. 



This is the first record of a Pionosyllis from southern waters carrying its embryos 

 on its back. 



