SEA-FISHERIES LABORATORY. 279 



sisting of almost identical notopodia and neuropodia each 

 ramus bearing capillary and furcate setae ; four dia- 

 phragms at the posterior end of the first, second, third and 

 fourth segments ; heart median ; a pair of slender, tubular 

 nephridia in each segment, except in a few of the anterior 

 ones. Burrowers, e.g., Scalibregma, Eumenia. 



(5) Chlorh^emidje. — Prostomium bears a pair of 

 grooved processes and several tentacles which act as gills 

 and are usually greenish, due to the colour (chlorocruorin) 

 of the contained blood ; capillary setee in all segments 

 except the peristomium ; those of the anterior segments 

 are directed forwards forming a protection for the head ; 

 limits of segments not clearly marked ; only one or two 

 internal septa present and a corresponding number of 

 pairs of nephridia. Burrowers in mud, e.g., Sipliono stoma. 



(6) Sternaspid.e containing the single genus Stern- 

 aspis ; body short, anterior region thickened and carrying 

 on each side three rows of setae ; on the ventral surface at 

 the posterior end there is a bilobed horny plate, round the 

 edges of which are some fifteen or sixteen tufts of long 

 setse, and dorsal to these two bundles of filamentous gills ; 

 the ends of the genital ducts project freely. 



The family Arenicolid^e contains two genera — 

 Arenicola and Branchiomaldane. The latter is, however, 

 only provisionally and doubtfully placed here, and as its 

 anatomy and affinities are so uncertainly known it may be 

 neglected in this account. The definition of the family 

 may, therefore, be taken as that of the genus Arenicola, 

 which may be summarised as follows : — 



Limnivorous Polychseta provided with numerous 

 pairs of branched gills not present on the anterior seven 

 segments. Prostomium small or moderately well 

 developed, bounded posteriorly by the nuchal organ, no 

 tentacles or palps. Parapodia each consisting of a conica] 



