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Genus Parahalosydna Horst. 



Horst, Zoolog. Mededeel. R. Museum Nat. Historie. Leiden, Vol. I, 191 5, p. 10. 



Characterised by the presence of only 15 pairs of elytra, on segments 2, 4, 5, 7, g. . . 

 23, 26, 28 and 30, covering the whole dorsum ;. notopodial fascicle rudimentary. , 



I. Parahalosvdna sibogae Horst. PI. XIX, figs. 6 and 7. 



Horst, Zool. Mededeel. R. Museum Nat. Historie, Leiden, vol. I, 191 5, p. 11. 



Stat. 105. 6°8' Lat. N., 121° 19' Long. E. North oft' Sulu Island. Depth 275 M. i specimen. 



At this Station a small Polynoid-worm was captured, that with regard to the structure of 

 its head and the rudimentary feature of its notopodia fully agrees with Halosydna, but only 

 possesses 15 pairs of elytra. The specimen is colourless and has a length of 12 mm.; the 

 number of its segments amounts to 34. The prostomium (PI. XIX, fig. 6) is elongated, longer 

 than broad, faintly notched in the middie of its lateral sides ; it is provided on each side with 

 a pair of large eyes, situated next to each other, in front of the posterior margin of the head. 

 The tentacle (unpaired antenna) arises with its basai part from the middie of the head ; it has 

 a filiform tip and it is smooth and about a third longer than the lateral antennae. These arise from 

 the lateral frontal corners of the head with a rather long, thick basal part and have a filiform 

 distal joint, that is twice and a half as long. The palps are very short, conical and smooth. 

 The first segment bears two tentacular cirri, tapering distally, the ventral of which is some- 

 what longer than the dorsal one. 



There are 1 5 pairs of elytra, covering the whole dorsum and overlapping each other 

 in the median dorsal line, situated on segments 2, 4, 5, 7, 9. . . . 23, 26, 28 and 30 ; each 

 elytron is faintly reniform, with a smooth surface except a group of small tubercles along its 

 concave side. Its margin is without appendages and its scar of attachment lies eccentrically 

 and is associated with a nerve-ganglion and numerous branching stems irradiating from it. 



The parapodia (PI. XIX, fig. 7) have only the neuropodial lobe well-developed ; this has 

 two oval lips and contains a fascicle of bristles, that have a smooth shaft and an enlarged, 

 wedge-shaped distal part, the latter being faintly bent and serrated along both edges. The noto- 

 podial lobe is rudimentary and besides the acicula contains only three small faintly serrated 

 bristles. The ventral cirrus is enlarged in its basal part and hardly reaches the extremity ot 

 the foot ; the dorsal cirrus however is very long, about four times the length of the bristle- 

 fascicle. At first it was supposed, that this species perhaps might belong to the genus Malm- 

 greiiia, that according to Mc Intosh should have lateral tentacles springing from the front 

 of the head as in Lepidonotits and fifteen pairs of elytra ; however it is afterwards stated 

 by GiARD and St. Joseph, that this has been a mistake and that the species Malmgr. cas- 

 tanea and andreapolis do belong to the Hannotlioinae, as sufficiently is demonstrated by the 

 figures of Mc Intosh himself. 



Neither can our species be ranged among the genus Ha/osydna, that according to 



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